non disruptive road crossings (1)

NON DISRUPTIVE ROAD CROSSINGS

MANUAL

DRAFT DOCUMENT

JANUARY 2013

NON DISRUPTIVE ROAD CROSSINGS MANUAL

Page i January 2013

January 2013

Draft Edition

Abu Dhabi Department of Transport

Al Bateen Towers

PO Box 20

Abu Dhabi, United Arab Emirates

© Copyright 2012, by the Abu Dhabi Department of Transport. All Rights Reserved. This

manual, or parts thereof, may not be reproduced in any form without written permission of

the publisher.


Page ii January 2013

TABLE OF CONTENTS

List of Figures .................................................................................................................................. v

List of Tables .................................................................................................................................. vi

1 Introduction .............................................................................................................................. 7

1.1 Overview ............................................................................................................................. 7

1.2 Purpose and scope .............................................................................................................. 7

1.3 Application of this manual .................................................................................................... 7

2 Non Disruptive Road Crossings Methods .............................................................................. 8

2.1 Non-steerable soil displacement methods ........................................................................... 8

2.2 Non-steerable soil removal methods.................................................................................... 9

2.3 Horizontal directional drilling (HDD) ................................................................................... 11

2.4 Micro tunnelling ................................................................................................................. 13

2.5 Pilot pipe jacking ............................................................................................................... 15

2.6 Manned pipe jacking methods ........................................................................................... 16

2.6.1 Open front pipe jacking techniques ............................................................................. 16

2.6.2 Closed front (full face excavation) pipe jacking techniques ......................................... 17

2.7 New NDRC Techniques..................................................................................................... 19

2.7.1 Easy Pipe ................................................................................................................... 19

2.7.2 Direct Pipe .................................................................................................................. 20

3 General .................................................................................................................................... 22

3.1 Overview ........................................................................................................................... 22

3.2 Standards and Codes of Practice ...................................................................................... 22

3.3 Roles and responsibilities .................................................................................................. 22

3.3.1 Client .......................................................................................................................... 23

3.3.2 Consultant .................................................................................................................. 23

3.3.3 Contractor/Sub Contractor .......................................................................................... 23

3.3.4 Road Authority ............................................................................................................ 23

3.3.5 Abu Dhabi Town Planning .......................................................................................... 23

3.3.6 Utility Agencies ........................................................................................................... 23

3.4 Process Map ..................................................................................................................... 23

3.5 Health and Safety .............................................................................................................. 26

3.5.1 At Concept Stage ....................................................................................................... 26


Page iii January 2013

3.5.2 Preliminary Design Stage ........................................................................................... 26

3.5.3 At Pre-Construction Stage .......................................................................................... 27

3.5.4 During Construction Stage .......................................................................................... 27

3.6 Environmental requirements .............................................................................................. 30

3.7 Site condition survey ......................................................................................................... 31

3.8 Geotechnical Investigation ................................................................................................. 32

3.8.1 Minimum requirements of the exploratory boreholes .................................................. 33

3.8.2 Borehole Positions...................................................................................................... 33

4 Procedures for undertaking non disruptive road crossings ............................................... 35

4.1 Overview ........................................................................................................................... 35

4.2 Concept Stage ................................................................................................................... 35

4.3 Preliminary Design Procedures ......................................................................................... 35

4.3.1 Method selection ........................................................................................................ 35

4.3.2 Design drawings ......................................................................................................... 58

4.3.3 Hand excavation ......................................................................................................... 59

4.4 Pre-construction stage ....................................................................................................... 59

4.4.1 Design calculations..................................................................................................... 59

4.4.2 Design drawings ......................................................................................................... 60

4.4.3 Ground Surface Movement ......................................................................................... 60

4.4.4 Groundwater Control .................................................................................................. 77

4.4.5 Materials and equipment ............................................................................................ 77

4.4.6 Method of statements ................................................................................................. 78

4.4.7 Risk Assessment and Risk Register ........................................................................... 80

4.4.8 Procedure and logistics for obtaining No Objection Certificates .................................. 81

4.5 During Construction ........................................................................................................... 81

4.5.1 Monitoring of Surface Movement ................................................................................ 81

4.5.2 Instrumentation Requirements .................................................................................... 83

4.5.3 Equipment Performance Requirements ...................................................................... 84

4.6 After Construction .............................................................................................................. 85

4.6.1 Inspection and testing ................................................................................................. 85

4.6.2 Site clearance and decommissioning ......................................................................... 86

4.6.3 Monitoring/inspection for long term (latent) defects .................................................... 86

4.6.4 QA/ QC Methodology ................................................................................................. 86

Appendix A: Checklists for submittals ........................................................................................ 88


Page iv January 2013

Appendix B: Forms and examples of letters for applying for NDRC works .............................. 92

Appendix C: Suggested minimum safe distances between utilities ........................................ 106

Appendix D: Checklists for monitoring during and after construction ................................... 107

Cited References ......................................................................................................................... 112

Other References ......................................................................................................................... 113

Glossary ....................................................................................................................................... 114


Page v January 2013

LIST OF FIGURES

Figure 1: Impact moling/soil displacement hammer ........................................................................... 8

Figure 2: Pipe ramming diagram (Earth Tool Company, LLC) ............................................................ 8

Figure 3: Impact moling ..................................................................................................................... 9

Figure 4: Auger head ....................................................................................................................... 10

Figure 5: Auger boring ..................................................................................................................... 10

Figure 6: Process of the horizontal directional drilling (HDD) ........................................................... 12

Figure 7: Micro tunnelling ................................................................................................................ 13

Figure 8: Slurry shield micro tunnelling (Iseki Poly-Tech, Inc.-japan) ............................................... 14

Figure 9: Stages of pilot pipe jacking with auger soil removal .......................................................... 15

Figure 10: Backactor shield ............................................................................................................. 16

Figure 11: A cutter boom shield ....................................................................................................... 17

Figure 12: Open front pipe jacking ................................................................................................... 17

Figure 13: A slurry shield (full face excavation) pipe jacking machine .............................................. 18

Figure 14: Earth Pressure Balance Machine (EPBM) ...................................................................... 18

Figure 15: Easy pipe Method ........................................................................................................... 20

Figure 16: Direct Pipe Method ......................................................................................................... 21

Figure 17: Process map of NDRC.................................................................................................... 25

Figure 18: Pipe jacking worksite and shaft ....................................................................................... 26

Figure 19: The different cutting heads ............................................................................................. 39

Figure 20: Principles of a hydraulic mucking boring machine (Herrenknecht documents) ................ 40

Figure 21: Locating systems ............................................................................................................ 45

Figure 22: Basic components of rig .................................................................................................. 46

Figure 23: Slanted face Drill Bits ...................................................................................................... 49

Figure 24: Modified Slanted face Drill Bits ....................................................................................... 49

Figure 25: Modified Slanted face Drill Bits ....................................................................................... 50

Figure 26: Rock Drill Bits ................................................................................................................. 50

Figure 27: Tri-Cone Rock Bits .......................................................................................................... 51

Figure 28: Experience guidelines for the application of different NDRC methods ............................. 55

Figure 29: Working shafts ................................................................................................................ 56

Figure 30: Stability Vs Volume Loss ................................................................................................ 66

Figure 31: Typical Settlement Profile for a Soft Ground Tunneling ................................................... 70

Figure 32: Assumptions for width of settlement trough (adapted from Peck, 1969) .......................... 71

Figure 33: Example of Finite Element Settlement Analysis for Twin Circular Tunnels under Pile

Foundations ..................................................................................................................................... 72


Page vi January 2013

LIST OF TABLES

Table 1: Parameters to be considered in relation to each soil type .................................................. 34

Table 2: NDRC methods related to soil types .................................................................................. 37

Table 3: Different applications of NDRC .......................................................................................... 38

Table 4: NDRC methods with typical pipe size, length and accuracy ............................................... 42

Table 5: Rigs types and specification ............................................................................................... 47

Table 6: Drill Bit Types and Application Guidelines (Courtesy DCCA) ............................................. 48

Table 7: Operational risks in HDD installations (Baumert and Allouche 2003) ................................. 54

Table 8: Design of working shafts in Dry ground .............................................................................. 56

Table 9: Design of working shafts in wet ground .............................................................................. 57

Table 10: Shaft Dimensions ............................................................................................................. 58

Table 11: Shaft sizes ....................................................................................................................... 58

Table 12: Relationship between Volumes Loss and Construction Practice and Ground Conditions . 68

Table 13: Risk summary for typical NDRC methods ........................................................................ 80

Table 14: Type of records for NDRC projects .................................................................................. 83


Page 7 January 2013

1 INTRODUCTION

1.1 Overview In 2010, the Abu Dhabi Department of Transport commenced with the “Unifying and Standardizing of

Road Engineering Practices” Project. The objective of the project was to enhance the management,

planning, design, construction, maintenance and operation of all roads and related infrastructures in

the Emirate and ensure a safe and uniform operational and structural capacity throughout the road

network.

To achieve this objective a set of standards, specifications, guidelines and manuals were developed

in consultation with all relevant authorities in the Abu Dhabi Emirate including the Department of

Municipal Affairs (DMA) and Urban Planning Council (UPC). In future, all authorities or agencies

involved in roads and road infrastructures in the Emirate shall exercise their functions and

responsibilities in accordance with these documents. The purpose, scope and applicability of each

document are clearly indicated in each document.

It is recognized that there are already published documents with similar objectives and contents

prepared by other authorities. Such related publications are mentioned in each new document and

are being superseded by the publication of the new document, except in cases where previously

published documents are recognized and referenced in the new document.

1.2 Purpose and scope The purpose of this Manual is to provide specific procedural guidance on Non Disruptive Road

Crossings (NDRC) for staff of the Abu Dhabi Department of Transport and other concerned

government highway agencies (Municipalities), designers, Contractors and utility agencies.

However, due to the specific technical nature of this type of construction, the Manual also provides

guidelines for the specialized Contractors experienced in the utilization of plant and equipment

fabrication, in order to select the most appropriate method for such operations.

The Manual is specifically aimed at recognizing local conditions related to the present legal

framework, existing geotechnical conditions and practices presently employed by the local

construction industry which perform successfully. However, global best practices are studied and

improvements recommended as appropriate.

The overall objective of this Manual is to provide guidelines for the construction of NDRC which do

not result in either short term or long term surface movement, nor in road collapse due to drilling

mistakes or obstacles.

1.3 Application of this manual The Manual is intended for use by the Abu Dhabi Department of Transport and other road agencies

of the Emirate (Municipalities) in specifying the requirements and approval procedures for NDRC

work.

It is however also to be used by utility agencies, designers and Contractors in selection and design

of NDRCs.


Page 8 January 2013

2 NON DISRUPTIVE ROAD CROSSINGS METHODS In this Chapter more detailed information is given on various methods of NDRC.

2.1 Non-steerable soil displacement methods A number of soil displacement methods exist. Impact moling or sometimes called soil displacement

hammer is one of the more common methods. The method involves driving a moling or hammering

tool with a tapered head through the ground (see Figure 1). The hammering tool can either work with

compressed air or hydraulically and it displaces the soil as it moves through the ground.

The piping or cable material is either pushed directly behind the tool or, in stable soil conditions it

may be pulled in afterwards through the cavity made by the tool.

Pipe ramming with a closed pipe is another soil displacement method often used. Like impact moling

or soil displacement hammer it uses compressed air or hydraulically activated ramming device to

push a closed steel pipe through the soil (see Figure 2).

Figure 1: Impact moling/soil displacement hammer

Figure 2: Pipe ramming diagram (Earth Tool Company, LLC)


Page 9 January 2013

Advantages and disadvantages of the non-steerable soil displacement technique are briefly set out

below.

Advantages

• Generally very quick and easy to use and thereby also very cost effective. Moles or

hammering tools are available for many soil conditions and can penetrate soft rock.

• The methods require relatively small entry and exit pits. When installing the pipe or cable

directly behind the hammering tool, surface settlements are minimised.

Disadvantages

• The methods require that the soil is displaceable and surface heave may occur if sufficient

soil cover is not available above the tunnel.

• A minimum cover of 10 times the outer pipe or hammer diameter is recommended.

• Pipelines installed in this manner are necessarily straight as there is no steering mechanism.

• The alignment of the tunnel can be influenced by the soil conditions, especially obstructions

or stratifications that may alter the direction of the tool or pipe.

• Installation of pipelines that require a precise alignment should not be undertaken using non-

steerable methods.

• The poor alignment accuracy also reduces the typical lengths for which the methods are

appropriate, and safe distances to other structures or utilities must be maintained.

Figure 3: Impact moling

2.2 Non-steerable soil removal methods Pipe ramming can also be carried out with an open pipe end and thereby without soil displacement.

Instead the soil is either removed during the driving of the pipe or afterwards. Soil removal is typically

undertaken using water jetting, flushing, compressed air or mechanically, for example with an auger.

These are some points to consider with this method:

• With the use of an auger, a cutting head can be attached to the head giving an improved

method for application in harder soils. Examples of pipe ramming and auger boring are

shown in Figures 8 and 9.


Page 10 January 2013

• The pipe material is usually a steel casing or sleeve pipe inside which the product pipe or

cables can be pulled or pushed after soil removal.

• Entry and exit pits are required for this method, where the entry pit may need to be very long

in order to accommodate the pipe and auger sections along with the ramming or jacking

device.

• Below ground water levels the methods must be used with caution or dewatering must be

initiated.

• Pipe ramming may be achieved if the pipe can be driven completely through before soil

removal and the soil "plug" inside the pipe is sufficiently stable to withstand the ground water

pressure while ramming.

When auger boring, the auger may become flooded underground water levels giving way for

excessive soil loss and major surface settlement. Some manufacturers have designed a sluice

system for the auger to counter this effect.

Figure 4: Auger head

Figure 5: Auger boring



Advantages

• These methods, like the other non-steerable methods, are generally less expensive than

similar sized steerable methods due to the need for fewer and simpler equipment and

machinery.

• The method can be used for significantly larger pipe sizes compared to displacement

techniques (2000 mm diameter or larger). The larger diameter pipelines are typically stiffer

and less susceptible to altering direction during installation.

Disadvantages

• In swelling or very plastic soils the methods may not be possible.

• Pipe ramming cannot be done in rock. However with the use of an auger, a cutting head can

be attached to the head giving an improved method for application in harder soils.

• Loss of face stability when tunnelling below groundwater level can lead to construction

difficulties and even failure to complete the tunnel. The same difficulties with directional

control exist as for the non-steerable methods.

2.3 Horizontal directional drilling (HDD) Horizontal direction drilling is likely to be the most widely used NDRC method, due to the extreme

versatility in uses. The method can be conducted from the ground surface without the need of deep

entry and exit shafts.

• The installation size can be anywhere from small diameter single cable crossings up to 1200

mm diameter pipes. Drilling distances can reach as much as 1500-1800 m in a single drill -

longer drills have been achieved using intersecting methods.

• The method requires a HDD rig capable of applying torque and thrust to drill a drilling pipe

through the ground. A steerable drilling head, specially designed for the soil conditions, is

situated at the front end of the pipes.

• Directly behind the drill head is a probe or transmitter sending signals through the ground.

These signals can be tracked from the ground surface, thereby determining the position and

depth of the drill. The direction of the drill can be altered by the asymmetrical steering face of

the drill head.

• After completing the drill, the bore hole is expanded to the required size by attaching reamers

to the drill pipe and pulling back in one or more steps. The desired pipeline is typically

attached directly behind the final reamer.

• Drilling fluid (typically a bentonite suspension) is continuously pumped into the borehole in

order to remove the spoils and support the borehole. An example of a HDD setup is shown in

Figure 6.

• The reamer is generally larger than the pipeline being installed creating an overcut or annular

space surrounding the pipeline through which the soil and drilling fluid mixture can escape.



Figure 6: Process of the horizontal directional drilling (HDD)

Advantages

• The wide size range and the ability to undertake HDD without large entry and exit pits and

without groundwater lowering are very clear advantages of this method.

• The direction of the drill can be altered while drilling making it possible to install a curved

pipeline. This can be a great advantage when manoeuvring around existing structures or

other utilities.

Disadvantages

• The achievable alignment accuracy may be insufficient for pipelines that require high

precision alignment.

• Maximum pipe diameters are limited to about 1200mm.



• Sudden changes in soil type from say clay to sand can lead to loss of control of fluid

pressure which in turn can lead to collapse of the soil annulus around the pipe.

• In certain situations, the pipe may become stuck leading to loss of the HDD string.

2.4 Micro tunnelling Micro tunnelling is a name generally associated to unmanned pipe jacking methods for pipes smaller

than 1000 mm diameter. However larger diameter machines and equipment are readily used and it

would be more appropriate to use the term micro tunnelling for any unmanned pipe jacking using a

steerable tunnelling machine.

Figure 7: Micro tunnelling

In micro tunnelling the pipeline is installed by pushing (jacking) the pipes forward from the starting

shaft as the tunnelling machine excavates the soil at the front of the pipeline. The excavated soil can

be removed through the already laid pipes by various methods. Examples of this are auger soil

removal or slurry shield micro tunnelling as shown in Figures 7 and 8.

In the auger method the excavated soil is removed mechanically with the continuous line of augers.

In the slurry shield method the excavated soil is mixed with a bentonite slurry suspension and

pumped out of the pipeline. After being pumped out the soil is settled or separated from the slurry in

a tank or separation unit and the slurry is reused.

When working below ground water levels the auger soil removal may pose the same problems,

where the auger may flood and give way for excessive soil loss. The slurry shield micro tunnelling

machine is typically designed with a pressurized bulkhead, where slurry is pumped at a sufficient

pressure to stabilizes any loose soil and balance ground water pressure.

The tunnelling machine can be controlled by an operator outside the pipeline. The alignment is

usually controlled by laser or by gyroscope and water level. The line is typically straight, but using



gyroscope or specialized surveying equipment and short pipe lengths, curved tunnels can be

constructed.

Piping materials must be designed to withstand the jacking forces acting on them under installation.

Concrete is often used as piping material along with fibreglass or composites with concrete and

fibreglass. Polymer materials especially polymer concretes are becoming more common due to there

strength and corrosion resistance.

Figure 8: Slurry shield micro tunnelling (Iseki Poly-Tech, Inc.-japan)

Advantages

• Micro tunnelling works in almost all soil conditions and cutting heads can be modified to deal

with weak rocks.

• Pipes of up to 2000mm diameter can be installed and can be constructed to a high degree of

accuracy which makes the technique suitable for pipelines that require precision in alignment

or gradient.

Disadvantages

• Obstacles (large rocks/boulders or other materials) may stop machines not designed for

cutting through these materials. In such cases there may be no other solution, than to

excavate from the surface to remove the obstacle. If this is not possible, the tunnel and

machine may have to be abandoned.



• Working in mixed face conditions can be problematic, particularly where slurry support is

used below groundwater as the slurry pressure may be difficult to control. Loss of slurry/face

support can lead to instability and ravelling leading to large surface settlements and, in the

extreme case, abandonment of the pipe and machine.

• Micro tunnelling is generally more expensive than many of the other NDRC methods,

requiring relatively large entry and exit shafts and more advanced equipment and materials.

2.5 Pilot pipe jacking This method is basically a variation of the non-steerable auger boring method. In this method

however a steerable pilot pipe is initially jacked or drilled through the soil. The alignment of the pilot

pipe is controlled by laser and a small camera at the head of the pipe.

After installing the pilot pipe an open steel pipe with an auger for soil removal is attached to the pilot

pipe and pushed/jacked through. The steel pipe is usually just used as a sleeve for the product pipe

which is pulled in afterwards.

Variations of the method include attaching a reamer followed by a plastic pipeline and pulling these

through in a similar manner as HDD.

Figure 9: Stages of pilot pipe jacking with auger soil removal



Advantages

• The method is very accurate (unlike the non-steerable auger boring method). The pilot pipe

can generally be installed to an accuracy of +/- 20 mm and the steel sleeve pipe will typically

follow this line with little deviation.

• The technique is a relatively cheap method of achieving a pipeline to a high precision in

alignment and gradient.

Disadvantages

• Large rocks or differences in soil structure surrounding the pilot pipe can give problems.

• Ground water may give some of the same problems described in sections on non-steerable

auger boring and micro tunnelling.

2.6 Manned pipe jacking methods Manned pipe jacking methods are very similar to the techniques given as micro tunnelling – the

difference is basically that the manned methods are sufficiently large in diameter to accommodate

workers inside the pipeline.

A wide range of tunnelling machines designed for varying types of soil and groundwater conditions

exist. The machines can generally be divided into open or closed face machines – the selection is

dependent on the soil conditions and the required support necessary for stability of the soil.

2.6.1 Open front pipe jacking techniques Open faced pipe jacking can be done in stable soil conditions with little or no ground water inflow.

The method consists of a tunnelling machine with an open front, where soil is excavated

mechanically and transported with conveyor belt and/or buckets out of the pipeline. Examples of

open front pipe jacking are shown in Figure 10 and Figure 11.

Figure 10: Backactor shield



Figure 11: A cutter boom shield

Figure 12: Open front pipe jacking

Working below ground water levels, pressure may be applied to the front using a chamber lock

system as shown in Figure 12. The pressurized front allows excavation without losing soil stability

due to ground water infiltration. This will generally only work in cohesive soils or rock - in very loose

soils, an open front is very questionable.

2.6.2 Closed front (full face excavation) pipe jacking techniques In loose soils or conditions with high ground water levels, a closed front machine may be used.

Closed front machines can be of the slurry shield type as described in Section 4.5 on micro

tunnelling or alternatively an earth pressure balance machine.

The slurry shield tunnelling machine works as described previously with a bentonite slurry

suspension that is mixed with the excavated soil and pumped out of the pipeline. An example of this

type of machine is shown in Figure 16.



Figure 13: A slurry shield (full face excavation) pipe jacking machine

Figure 14: Earth Pressure Balance Machine (EPBM)

Advantages

• Manned pipe jacking methods have the general advantage that access to the driving front is

relatively easy - making it possible to remove obstacles (larger rocks/boulders etc.) with

manual methods.

• Open front machines obviously have the most direct access, where closed front machines

may need to be designed with access gates.

Disadvantages

• There are many health and safety issues associated with manned pipe jacking, not least the

need to work in confined spaces with the dangers of face collapse and groundwater

inundation.

• Detailed and robust health and safety procedures dealing specifically with the hazards

related to this construction method need to be implemented for all manned pipe jacking

operations.



• Tunnelling equipment is large and expensive and requires relatively large site areas for the

launch and reception pits.

2.7 New NDRC Techniques NDRC techniques continue to evolve and new techniques are constantly being trialled and

implemented to overcome some of the disadvantages of conventional techniques or provide faster,

cheaper installations. Two such techniques are the “Easy Pipe” and the “Direct Pipe” methods

2.7.1 Easy Pipe This technique combines conventional micro tunnelling with an innovative method of using the

jacking pipes to help install the permanent pipe. Once the tunnel has been bored, the micro

tunnelling machine is removed and the permanent pipe is attached to the installed jacking pipes.

The jacking pipe segments (which are bolted together) are pulled back through the tunnel, pulling the

permanent pipe with them. In this way, the permanent pipe is installed quickly and easily and the

jacking pipe segments can be re-used for the next project.

Easy Pipe installation requires a micro tunnelling unit to be prepared and assembled in the launch

pit. The cutter head is launched and guided in the conventional micro tunnelling way along a planned

alignment.

The difference between the jacking pipes used by Easy Pipe and conventional ones is that the

special design allows them to be used as jacking pipes in the forward direction while allowing them

to be retracted from the completed bore to pull in the product pipe.

This is because the joints between the jacking pipe sections bolt together with a design that will

withstand thrust and pullback forces of up to 6,300 kN (630 tons).The close proximity of the jacking

pipes' outer wall to the bore wall also avoids the potential for collapse of the bore in unstable ground

formations.

After the cutter head has reached the target pit, it is separated from the jacking pipe string and

replaced by a specially designed connection pipe that also connects to the product pipe. The jacking

pipes are then pulled back using the bi-directional jacking frame, simultaneously pulling the product

pipe into position. In the launch pit the individual jacking pipes are successively removed along with

all other equipment until the product pipe arrives at the launch shaft.

The connection pipe and jacking frame are removed from the pit leaving the product pipe in place to

be finally connected to the remainder of the pipeline on either side of the obstacle(s) crossed.



Figure 15: Easy pipe Method

2.7.2 Direct Pipe The direct pipe technique is a hybrid of the HDD and micro tunnelling methods. In this technique, the

micro tunnelling machine is pushed in to the ground using a jacking frame that grabs directly on to

the final production pipe and uses this to push the micro tunnel machine forward. In this way, once

the tunnel is bored, there is no need for a secondary production pipe installation process as the

production pipe is installed directly as part of the tunnelling operation. Installation of the pipe is

limited by the thrust that can be applied to the pipe without causing damage and the need for

sufficient space to lay the pipe out behind the micro tunnel machine prior to commencing boring.



Figure 16: Direct Pipe Method

Advantages

• Single-step method leads to rapid installation of product piping and pipelines

• No time needed for coupling pipes (Micro tunneling) or drill rods (HDD)

• Pipeline can be installed pre-welded and already tested

• Costly shaft construction unnecessary - instead, only simplified surface entry and exit pits are

required

• One-pass work phase of operation for excavation and pipeline installation

• Inclines and gradients as well as curved drilling profiles can be negotiated precisely

• Ideal method for sea outfalls with access from one side only

• Pipe Thruster enables both tunneling machine and pipeline to be withdrawn, for example for

cutting tool retooling operations in inaccessible, low-diameter areas

• Cone crusher removes obstacles as they occur

Application options

• Pipeline laying from construction pit to construction pit

• Pipeline laying from construction pit to shaft

• Pipeline laying from construction pit to destination point, for example water course beds

Range of application

• Pipeline diameter: - 28” - 36” 38” - 44” 46” - 52” 54” - 60”

• Excavation diameter 805 / 990 mm 1,140 mm 1,325 mm 1,540 mm

• Maximum pipeline / drilling length 300 m 700 m 1,200 m 1,400 m

• Geology: - Clay, Silt, Sand, Gravel, Cobbles, Boulders, Rock (up to 150 Mpa = 21,750 psi)

• Pipe material: - Steel

• Coating material: - . PE, PP, GRP, FBE



3 GENERAL

3.1 Overview This chapter provides general information for undertaking Non Disruptive Road Crossings including

an overview of the parties involved and their roles and responsibilities.

The chapter further covers the general requirements for environment, health and safety along with

requirements for site survey and geotechnical investigations.

3.2 Standards and Codes of Practice A number of local and international Standards and Codes of Practice along with guidelines and

specifications have been sourced during the process of creating this manual. The documents and

information listed below were chosen as they are typically viewed as being ‘best practice’

internationally, in the field of NDRC and trenchless technology. Particular reference can be made to

the following existing key documents:

• Abu Dhabi Municipality Road Department - Requirements and Recommendations for Non -

disruptive Road Crossings

• Abu Dhabi Municipality Sewerage Projects Committee - General specifications for civil works,

Pipeline construction by Non disruptive method (2003)

• The Pipe Jacking Association (UK) - "An introduction to pipe jacking and micro-tunnelling

design" (1995)

• Horizontal Directional Drilling Good Practices Guidelines - 2008 (3rd Edition) USA

• Standard DWA-A 125E Pipe Jacking and Related Techniques, German Association for

Water, Wastewater and Waste. (2008)

• Microtunneling and Horizontal Drilling Recommendations, FSTT, French Society of

Trenchless Technology (2006)

• Euronorm EN 12889: Trenchless Construction and Testing of Drains and Sewers.

• There is a wealth of globally available documentation about 'trenchless' or 'no dig' technology

and the list above covers some of the more important ones. Additional information on

methods and equipment can be found in these or from technical associations such as:

• International Society of Trenchless Technology, ISTT - www.istt.com

• Pipe Jacking Association (UK) - www.pipejacking.org

• North American Society for Trenchless Technology, USA - www.nastt.org

3.3 Roles and responsibilities This section describes typical roles and responsibilities of the parties involved in undertaking NDRC

works. The specific responsibilities and authorities of the different parties involved can vary from

project to project depending on the contract agreements between the parties.

Road crossings and in particular NDRC works are typically contracted as part of a main project

involving installation of utility lines in an area, along roads, etc.



3.3.1 Client The Client is the owner of the pipeline or cable to be installed. The overall responsibility for the

installation and operation of the pipeline or cable is that of the Client.

The Client can delegate certain responsibilities such as design and calculations along with the

responsibility for safeguarding of the road to others through contract agreements.

3.3.2 Consultant The Consultant is typically hired by the Client to design, tender and supervise the overall project.

The Consultant will typically undertake preliminary site and soil investigations to collect information

on existing utilities, surface and sub-surface constructions during the design stage. The consultant

will supervise the installation and NDRC work during construction.

3.3.3 Contractor/Sub Contractor The Contractor or, if delegated, the specialist Sub Contractor is responsible for the correct

installation of the pipeline or cable in accordance with the specifications.

The Contractor/Sub Contractor is responsible for obtaining approval from the Road Authority prior to

commencement of the NDRC work. Approval is only given after Submitting a complete and

acceptable method statement including all required information in accordance with this manual.

3.3.4 Road Authority The Road Authority (Abu Dhabi Department of Transport or any Municipality) is responsible for

giving approval of any NDRC work. The Road Authority's main interest is in protecting their assets -

the road, footpaths, structures, etc. from any harm, settlement or heave resulting from the NDRC

work which lies within the highway Right of Way.

3.3.5 Abu Dhabi Town Planning Abu Dhabi Town Planning will give initial approval and assign a corridor that the Client may use. This

is done only after checking with, and obtaining NOCs from the Road Authority, other Utility Agencies

and any other relevant authorities.

After giving approval and assigning a corridor Abu Dhabi Town Planning will refer to the Road

Authority for final approval of the NDRC work.

3.3.6 Utility Agencies Other utilities agencies may be affected by the NDRC if their pipelines or cables are located near the

proposed NDRC. The Contractor will need to obtain No Objection Certificates (NOC's) from all the

concerned utilities agencies. These may be accompanied with certain requirements or restrictions

concerning the NDRC.

3.4 Process Map When following the procedure below, it is imperative that the Consultant follow the guidance

contained in this Manual, and if any of the processes are not completed to the DoT’s satisfaction,

then the relevant stage will not be approved.



The process of undertaking NDRC work involves a five part approval process. Important points for

the Consultant to consider:

• The stages are illustrated in Figure 17 below showing the main activities and responsibilities

in each stage.

• Detailed information and requirements of the various activities can be found the subsequent

sections of this manual.

• Check lists of required submittals to the Road Authority are given in Appendix A.

• The estimated processing times in the approval stages are based on complete and full

submittals. Any missing information may result in prolonged processing times.

• Anywhere along the process factors may arise that will require the planned NDRC to be

revised and the process to be returned to an earlier stage.

• All applications for approval with the DoT must be submitted using the No Objection

Certificate - Right of Way (NOC-ROW) online system. Please refer to the DoT website for

the latest information on this subject.



Figure 17: Process map of NDRC

Responsible Activity Details and information to be acquired

PHASE 1 Concept Stage

Client/ Consultant

Map of intended NDRC Location/vicinity Size (diameter) and level

Approval process - part 1

Submit to Abu Dhabi Town Planning for approval of corridor and NOC Expected processing time: 4-6 weeks

PHASE 2 Preliminary design

Client/ Consultant

Geotechnical Geotechnical Assessment (Key stage 2) according to Manual for Geotechnical Investigation and Geotechnical Design including Ground Investigation Factual and Interpretative Reports.

Site investigation Surface and underground structures

Other utilities Location and type

Drawings Line, level, diameter Work area with working shaft locations and sizes

Method selection Suggested method and equipment Requirements for accuracy, material, etc.


Submit to Road Authority for preliminary approval of design Check list of submittals required is given in appendix A.

Expected processing time: 2-3 weeks

PHASE 3 Pre-construction Stage

Contractor/ Sub Contractor

Design calculations Pipe strength Working shafts Jacking and friction forces Surface settlement/heave

Design drawings Plans and profiles of the intended line Working area plans showing placement of equipment and materials. Traffic diversion plans Details of working shafts De-watering system design

Materials and equipment Lists of all in use

Method statement Contractor name List of personnel with qualifications Sequencing and procedure of work Ground water control and dewatering Safety procedures Environmental assessment Risk assessment

NOC From all relevant utilities and authorities

Letters of undertaking From Client and Consultant


Submit to Road Authority for approval of construction List of submittals required is given in Appendix A

Expected processing time: 3-4 weeks

PHASE 4 Construction

Contractor/ Sub Contractor

Site condition survey Surrounding surfaces and structures Pre construction photos

Monitoring Setup and monitoring of surface movement

QA/QC Documentation in accordance with QC plan

PHASE 5 After construction

Monitoring Surface movement - monthly reports



3.5 Health and Safety All parties involved in NDRC work have an important role in establishing safe working conditions.

During planning and design all foreseeable health and safety risks likely to arise shall be identified

and taken into consideration in the design. All health and safety information known to the Client,

Consultant or designer must be given to the Contractor prior to undertaking the NDRC work.

Figure 18: Pipe jacking worksite and shaft

The Contractor must ensure that prior to commencement of any project, a Health and Safety Plan is

prepared which covers the specific requirements of the project. This plan shall be submitted prior to

approval of construction along with the Method Statement, and approved by the relevant Consultant

(usually the Engineer).

General requirements for Environment Health and Safety must comply with the EHS Manual for

Road Projects. All issues relating to EHS must be raised and addressed along all stages of the

project.

3.5.1 At Concept Stage During this phase, it is important for the design team to establish the route of the NDRC to minimise

the risks to safety for any persons working on the construction.

When submitting the relevant design information to Abu Dhabi Town Planning, the Consultant must

take into account the safety impacts of the size and material used in the NDRC works, if they are

available at this stage.

3.5.2 Preliminary Design Stage During this phase, the designer must take into account:

• The specification of materials

• The location of the crossing – to minimise the safety impact on pedestrians, motorists and the

general public

• The diameter – to minimise the impact of construction works for construction personnel

• The ground conditions – to establish the risks of stability of the surrounding soils.



3.5.3 At Pre-Construction Stage This is an important phase for safety considerations as it maps out the construction processes and

methods via the Method Statement. The appointed Contractor should submit:

• A Method Statement which should detail all the construction methods and programme

• A Risk Assessment highlighting ALL risks to safety, rating each in terms of probability and

severity

• A Site Emergency Plan to show evacuation procedures in an emergency

• A Traffic Management Plan to set out the specific requirements for the site.

3.5.4 During Construction Stage During this stage there are many considerations for the Contractor to consider.

• A daily checklist for inspection of the works is included in the Appendix and this is to be

checked back and corroborated with the Method Statement.

The worker should take the following general precautions:

• Do not take chances that may lead to injury

• Either use tight sheet shoring to guard against the caving in of sandy soil or loose material

when the depth of the excavation exceeds 5 ft, or cut back the bank to the proper slope.

Keep shoring at or near the bottom of the ditch as it is excavated and follow with bracing to

ensure safety. Trench shields are also acceptable as a protective system. A trench shield

does not protect the environment, only the worker.

• The placement of shores will depend on the type (classification) of soil encountered. Local,

state or provincial, and federal laws man - date the distances and sizing of shoring support

systems.

• Extend shoring of any type below the excavation bottom whenever possible, and brace it

thoroughly using timbers, wedges, and cleats, or a pipe/screw-jack combination. Place all

bracing at right angles to the sheeting or uprights and rigidly wedge, bolt, or cleat it to prevent

movement. Hydraulic units are being used in many types of utility-trench construction

• Use only full-sized lumber that is assessed to be sound and straight.

• Install the upper braces or screw jacks first, and remove them last for best protection.

• Also consider excavation dimensions, soil stability, variable weather and moisture conditions,

proximity of other structures, weight and placement of soil and equipment used on the job,

and sources of vibration when choosing the type of shoring to use, if any. The decision must

rest with the engineer or foreman in charge.

• Use hydraulic jacks temporarily only, and replace them with properly sized screw jacks or

solid bracing.

• Personnel should not be required to do heavy lifting that may cause injury; use mechanical

lifting devices to raise, lower, or suspend heavy or bulky material when working in trenches,

manholes, or vaults.

• Use ladders where required. Do not jump into an excavation.



• Provide an adequate means of trench exit, such as a ladder or steps. Locate it so no more

than 25 ft of lateral travel is required. Extend the ladder from the bottom of the excavation to

at least 3 ft above the ground surface.

• Do not place excavated material closer than 2 ft from the edge of an excavation.

• Keep all tools, working materials, and loose objects orderly and away from the excavation

shoulder.

• Keep tools, equipment, and excavated material out of open traffic lanes.

• Take work breaks, rests, etc. at designated locations away from the excavation.

• When resuming excavation after heavy rains or freezing weather, inspect all banks for

cracks. These may indicate earth movement and the probability of cave-in.

• Frequently inspect the sides and rim of all open excavations to guard against cave-in.

Operate earth-moving equipment from a position that will not imperil personnel or property by

a cave-in due to vibration, stress, or dead weight.

• If it is absolutely necessary to work above an overhanging bank, use a safety belt and a

lifeline. Have a helper nearby to assist in an emergency.

• To avoid striking electric or telephone conduits, gas lines, or other sub-structures, locate

other utility installations before starting work.

• Require workers to wear adequate eye, ear, and foot protection when using a jackhammer or

when exposed to flying particles or falling objects.

• Workers should always be aware of locations of running machines (back–hoes, trenching

machines, etc.). Workers should keep clear of the sweep path and try never to turn their

backs toward the working machine(s).

3.5.4.1 Pipe storage • Keep pipe yards and walkways clean and orderly.

• Always block pipe to prevent it from rolling or falling.

• Arrange and block each row of stacked pipe to prevent it from rolling from the pile.

• Store small pipe in racks according to length and size.

• Store pipes larger than 2inch diameter by stacking them with spacing strips placed between

each row.

• Withdraw pipe from the top rows.

3.5.4.2 Shoring and bracing • Use proper shoring and bracing to prevent cave-ins while vaults or similar openings are

under construction.

• Proper shoring cannot be reduced to a standard formula.

• Each job is an individual problem and must be considered under its own conditions.

3.5.4.3 Posting barricades and warning signs • Place advance warning, instructional signs, barricades, and delineators well ahead of the

construction area to warn motorists and pedestrians of the area and safely take them through

or past it.



• Protect the work area with barricades, barriers, or planks to provide a safe working space. If

necessary, use flaggers to direct and slow down traffic. When used, place trucks or air

compressors between the work and the traffic.

• During periods of reduced visibility, use adequate lighting on all barricades.

• When no work is in progress, place adequate barriers, barricades, flashing lights, and signs

to warn and divert traffic. Use reflecting tape on all barricades.

• All personnel should wear protective clothing including hard hats and high visibility traffic

vests.

3.5.4.4 Trenching machines The following rules apply equally to all mechanical devices used to dig trenches and/or make

excavations including various types of trenchers, buckets, scoops, and similar pieces of equipment:

• Operators should always wear hard hats.

• Never attempt to oil or grease a mechanism or repair or adjust any moving part of a trenching

machine while it is in operation. Only qualified personnel should operate a trenching

machine.

• Guard all moving parts. Before starting the conveyor, make sure that no person is

endangered by it.

• To remove obstructions from the conveyor mechanism or buckets, stop the machines.

• Be alert for falling material that might roll from the conveyor.

• When practicable, drop dirt between the excavation and the high-way to act as a barrier.

• Cautiously fill gasoline or diesel tanks. Keep spout in metallic contact with the machine to

prevent static sparks from bridging the gap and igniting the vapours. Do not smoke. Keep

proper fire extinguishers available when refuelling construction equipment. Use only

approved containers when storing flammables on the job site; clearly mark and define

storage areas.

• Use flags by day and flashing lights or flares by night to warn the public of the trenching

machine and its operations. Liberally use these precautions on all highway or street work.

Plan the warning system before the work is started.

• Operate the machine vertically to prevent undercutting the trench wells.

• When loading or unloading trenching machines or other heavy equipment from truck beds,

lowboys, or other conveyances, provide suitable skids and ample blocking to prevent

movement of the conveyance

• When manually lifting or lowering pipe in an excavation, use two or more rope slings looped

under the pipe and handle from each side of the excavation. To prevent a heavy pipe from

pulling workers into the excavation, anchor one end of each rope sling to a massive object

such as a truck.

• When aligning pipes in the excavation, either manually or mechanically, keep hands and

fingers away from ends of pipe and other substructures that could crush.

• Govern crane operations only by the signals of a qualified worker.

• Never try to catch and hold a length of pipe that slips from a crane or hoist sling.

• Be alert to unsafe excavation sides when measuring, testing, or inspecting pipe in place on

an excavation bottom.



• When cutting sections of pipe, keep feet in the clear and use adequate blocking, chocks, etc

to prevent pipe movement.

• Wear safety goggles

• Keep tools and appliances in good condition for handling, cutting, threading, or treating pipe.

Always use the right tool for the job.

• Do not let tools or materials become stumbling hazards where pipe is being handled.

• Avoid shortcuts and makeshift methods that may increase the hazards of handling pipe.

Accidents and risks that may be particularly related to NDRC work will include, but are not limited

to:

• Falling accidents (deep excavations and shafts)

• Materials falling from a height

• Collapse of excavation or shaft

• Road collapse or failure

• Flooding from broken pipelines or groundwater

• Striking other utilities (power, gas, oil, water, etc.)

• Suffocation due to inadequate fresh air supply (manned pipe jacking or micro-tunnelling)

• Dangerous gasses

• Rotating and moving machinery and equipment

These along with any other risks must be assessed in the

Health and Safety plan including mitigation measures.

Employment of workers inside pipe jacking or micro tunnelling

pipelines shall not be permitted for pipelines with an internal

diameter smaller than 1.2 m.

The Contractor shall develop an emergency plan that describes

actions to be taken in the event of any sudden surface

settlement or collapse. This plan shall be included in the

Contractors method statement.

3.6 Environmental requirements General environmental requirements for any construction works in connection with main roads,

including undertaking of NDRCs, can be found in the EHS Manual for Road Projects.

Prior to commencing any projects an environmental permit must be acquired from The Environment

Agency - Abu Dhabi (EAD). Points that will need to be addressed for the environmental permit may

include:

• Soil or spoil removal including slurry handling and disposal.

• Dewatering including discharge.

• Waste management.

• Handling and storage of any hazardous materials.

• Activities creating dust, air pollutants or odours.

• Noise or vibrations.



• The Contractor is responsible for establishing, operation and decommissioning of the work

site in an environmentally safe way and this can be controlled by using a daily checklist

report which will be followed in line with the Method Statement. Such details will be included

in the Contractor's Method Statement.

• All waste materials shall be collected and disposed of in an appropriate manner, and the site

shall be cleared and void of any waste matter after the construction is completed.

• All materials and equipment shall be stored in accordance with manufacturer's guidelines and

in a way so that spills or emissions are avoided.

• Drilling fluids (slurry, bentonite, etc.) shall be recovered for

reuse or disposal at an approved location in accordance

with the environmental permit.

• The environmental issues that typically concern HDD

include:

- Access restrictions due to wetlands, streams,

endangered plant or animal life, endangered

habitat, and potential erosion

- Oil and fuel spills from construction equipment

- Drilling-fluid surface spills that endanger animal and

plant life

- Drilling fluid returns in water bodies

- Groundwater contamination from drilling-fluid

additives

- Drilling-fluid disposal locations (The contractor must obtain approval to dispose of the

drilling fluid at an approved disposal location. Bentonite is a good product for sealing

drainage ditches, irrigation reservoirs, and livestock ponds.

• However, approval must be obtained from EAD permit received for the works.

3.7 Site condition survey A site condition survey shall be conducted during both the preliminary design and construction

stages of the proposed NDRC. All surface and subsurface construction within a minimum of 30 m

from the proposed centreline and any shafts must be identified and the exact location determined.

These will include, but are not necessarily limited to:

• Cables, pipelines, sewers and manholes

• Pavements, footpaths, etc.

• Buildings

• Foundations, retaining walls, etc.

• Artificial cavities

• Constructional systems that have remained in the area along with any other structures or

systems that may have impact or be influenced by the intended NDRC.

A building and structure assessment plan documenting the condition and including photographs of

any existing damage must be included in the site condition survey. This shall be submitted for

approval of both the preliminary design and final design. In connection with the final design the site



survey must be reviewed and approved by the DoT road maintenance consultant and approved by

the DoT.

Immediately prior to construction the site survey shall reviewed by the Contractor and any changes

in the condition of buildings, structures, roads, footpaths and other paved areas shall be recorded

and photographed.

3.8 Geotechnical Investigation The geotechnical investigation shall be conducted in accordance with the Manual for Geotechnical

Investigation and Geotechnical Design including determining the projects geotechnical category and

the procedures for managing geotechnical risk as described.

Evaluation of soil conditions on NDRC projects is critical, but often under-emphasized. Success or

failure is intricately tied to correctly matching equipment and methods to soil Conditions. It is the

designer's responsibility to ensure that sufficient geotechnical information is available for the

complete design and safe installation of the NDRC.

For all NDRC work, a minimum requirement of a desk study shall be carried out, assessing the

available literature, maps, aerial photographs, utility plans and existing site investigations. The aerial

photographs must encompass as much historical information as possible, that show for example

lowlands swamps which have since been backfilled. Existing geotechnical investigations may be

acquired from the road department, adjacent building owners or structures and other utilities

agencies.

If insufficient geotechnical information is available for the area where an NDRC is proposed, then a

thorough geotechnical investigation must be conducted.

The soil investigation analysis is necessary for:

• Selecting the appropriate NDRC method, jacking technique and jacking works

• Selecting and designing the supports for launch and reception shafts

• Selecting and designing jacking pipes

• Planning measures for soil improvement in unstable soils

• Planning of soil disposal (landfill, treatment, recycling)

• Planning of measures for the control of groundwater

The field exploratory techniques selected should be appropriate to the type of ground and the

planned depth of the NDRC. The laboratory testing programme should include tests relevant to the

ground conditions and the NDRC techniques likely to be

employed. Table 1 below suggests parameters to be

considered in relation to each soil type.

The soil conditions shall be investigated and documented in

accordance with the Manual for Geotechnical Investigation

and Geotechnical Design. The investigation should result in

information on reliable soil parameters which are necessary

for the adequate design of the drives, shoring, and

dewatering details. Analysis and design (calculations for



jacking forces, stress analysis on the pipeline, ground surface settlement and heave analysis, etc.)

should be based on such parameters.

3.8.1 Minimum requirements of the exploratory boreholes Number of boreholes:

• 2 exploratory holes for crossings less than 25 m (one

at each end)

• 3 exploratory holes for crossings greater than 25 m

(each end and centre)

• Additional holes for long crossings or in areas with

difficult soil conditions (layered)

Depth of boreholes:

• Down to 2 m below pipe invert in groundwater free

soils

• Down to 3 m below pipe invert in groundwater bearing soils

• Down to the planned bottom edge of sheeting in the area of launch and reception shafts.

3.8.2 Borehole Positions Exploratory borehole positions should be chosen to provide information on the nature of the ground

that will be encountered by the NDRC. Under no circumstances should boreholes be sunk on the

line of the NDRC.

All boreholes should be properly backfilled and sealed. Piezometers should be installed where

recommended. Boreholes should always extend sufficiently far below the invert level to identify

changes in the strata below the NDRC that could affect both the construction and long term impact

of the NDRC. Boreholes should be sunk adjacent to shaft locations. Additional boreholes should be

considered, if required, to identify the location of significant changes in geology or to resolve other

geotechnical uncertainties.

All geotechnical investigations shall be carried out by qualified personnel and in accordance with The

Manual for Geotechnical Investigation and Geotechnical Design.



Table 1: Parameters to be considered in relation to each soil type

Test Non-

Cohesive Soils

Cohesive Soils

Mixed Soils

Fill Material

Rock

Unit weight and moisture content

X X X X X

Angle of friction X X X

Particle size distribution X X X X

Abrasivity X X X X X

Cohesion X X X

Types and proportions of minerals

X X X X X

Standard penetration tests X X X X

Permeability and nature of ground water level and flows (seasonal/tidal changes)

X X X X

Toxic/hazardous constituents in the ground/groundwater

X X X X X

Frequency and physical properties of boulders, cobbles or flints

X X X X X

Pump down tests X X X X

Presence of gases X

Compressive strength X

Rock quality designation (RQD)

X

Core logging (TCR, SCR, FI)

X

Tensile strength X

Specific energy (excavatability)

X

Slake durability X

Geological description X X X X

Plasticity indices (LL, PL, PI)

X X

Source: An Introduction to pipejacking and microtunnelling design



4 PROCEDURES FOR UNDERTAKING NON

DISRUPTIVE ROAD CROSSINGS

4.1 Overview This chapter contains the general procedures and requirements for undertaking any NDRC works

under DOT roads. It is divided into sections relating to the process map described in Chapter 1.

4.2 Concept Stage At this early stage, the concept of each project will be considered by the Designer, and as per the

stage gateway process, the options will be considered from a financial and environmental impact

point of view before progressing to the next stage. This will be in line with the requirements of Town

Planning as detailed in Chapter 2.

For NDRC, if applicable the impacts will be established and examined, and put forward into the

report generated by the Consultant. Depending on the project, it may be the case that different

routes for the NDRC are considered.

4.3 Preliminary Design Procedures

4.3.1 Method selection In this section more detailed information about the guidelines requirements and criteria related to the

two major NDRC methods are currently used in emirate of Abu Dhabi are given in order to help

select a method appropriate for the given project. More information on the various methods can be

found in Chapter 2.

The Client/Consultant should, before tender, determine which methods may or may not be used for

the NDRC works. The selection should be appropriate for the intended installation and meet the

requirements of this Manual. Method and equipment should be selected to avoid ground loss and

minimize settlement or heave. Also, a geotechnical section along the drive path shall be provided

with the ground surface and groundwater elevations shown. This will assist in determining the

method.

The selection of route and method shall be based on the information gathered during the site

investigation and geotechnical survey along with all other relevant information. The line and level of

the route shall be selected so as to avoid driving through weak/strong soil boundaries, weathering

interfaces and groundwater surfaces.

The methods presently available are many and diverse and new techniques are continually being

developed. Existing methods and equipment are becoming more advanced and variations or

combinations of different methods are also being developed.

The selection of method is also dependant on the:

• Cost – The cost of construction can vary dramatically depending on the method, materials,

and route chosen.



• Traffic Impacts – Designers and Contractors need to consider the negative effects on short

term traffic flow impacts

• Depth – The depth of the crossing as a wider effect on the extent of trenching required and

safety of personnel.

• Risk to surrounding utilities – Alternative methods should be considered when there is a large

impact on any surrounding apparatus. Risks should be assessed.

• Groundwater impact – The level of ground water can affect the ability to construct in a safe

and efficient manner.

• Required installation speed – Due to construction constraints it may be required to carry out a

fast installation. If so, the most appropriate method should be chosen.

• Settlement risks – Depending on the soil type encountered, the risk of settlement of the soil

may be high – this should be taken into consideration.

• Pipe size – The size of the pipe crossing effects the depth and type of construction chosen.

• Length of crossing – The length of the pipe is a strong deciding factor in the type of

construction to adopt.

• Required accuracy – All crossings must follow the route decided, however in some cases it

may be that a method is chosen where the required accuracy is not as high as others.

• Feasibility of open cut – It may be the case that an open-cut dig is found more appropriate.

This will be decided early on in the process.

Below is a Table 2 detailing NDRC methods depending on the different soil types.

Below is a Table 3 shows detailing the different applications for NDRC works and the options for

alternative construction methods:



Table 2: NDRC methods related to soil types

Parameter Impact Molling Pipe

Ramming

Guided HDD

Systems Mini

Guided HDD

Systems Midi

Pilot Pipe Systems

Hard rock X X X X X

Soft rock X X ◙ X X

Hard clay X X ◙ X X

Soft soils • • • • •

Sand & gravel X ◙ ◙ X X

Sand • • • • •

Cobbles/boulders X X X X X

Obstructions X X X X X

Below water table • X • • ◙

Parameter Auger Boring Directional

Drilling

Tunneling Pipe

Jacking

Micro-tunnelling

Auger

Mircrotunnelling

Slurry & EPB

Hard rock X • ◙ X ◙

Soft rock ◙ • ◙ X •

Hard clay • • • • •

Soft soils ◙ • ◙ ◙ •

Sand & gravel X ◙ ◙ X •

Sand ◙ • ◙ • •

Cobbles/boulders ◙ ◙ ◙ X ◙

Obstructions • ◙ ◙ X ◙

Below water table • • X X •

X – Not Suitable • - Suitable ◙ - May be Suitable (depends on specific circumstances)



Table 3: Different applications of NDRC

Micro tunnelling and Horizontal Directional are the most used methods in Emirate of Abu Dhabi, so

more discussion will be explained.

4.3.1.1 Micro tunnelling Method All types of Micro tunnelling boring machines have the following functions in common.

Mechanized ground excavation and stabilization of the face

• The head of the machine is equipped with a cutting wheel whose tools are used to last the

soil under the combined action of rotation and thrust. A crushing cone located behind the

cutting wheel and intended to reduce the size of larger elements to allow their mucking, is

present on most machines. There exist different cutting heads for various types of soil. (see

figure below). They can be distinguished by their cutting tools.

• For sandy or gravely soil, the cutting wheels are equipped with teeth (figure –a). In rugged

soil, these teeth dislodge the blocks, which are then crushed.

Utilization Auger

Boring

Directional

Drilling

Tunnelling Pipe

Jacking

Micro-nnelling

Auger

Mircro-tunnelling

Slurry & EPB

Cables U ø U U U

Flexible

Conduits

U ø U U U

Gas lines U ø U U U

Oil lines U ø U U U

Potable water U ø U U U

Force mains U ø U U U

Gravity mains U S ® ® ®

Gravity

Sewers

U S ® ® ®

Suitable at appropriate diameters and lengths ® - Small diameter only ø - Small diameter only U – Typically for Crossings only S – Siphon crossings only



Figure 19: The different cutting heads

• For coherent soil (silt, clay ,marl)the cutting wheels are fitted with tools which cut out chips of

soils (see figure –b).on some machines ,high pressure water jets are sprayed on the wheels

and in the stope to prevent sticking of clay and clogging of the mucking system.

• Finally for rocks (see figure –c)the cutting heads are equipped with rotary cutters having

small openings .with the help of the thrust ,the rotary cutters crush the rocks by means of

shear and tensile stresses, which create cracks and loosen the fragements.these machines

can bore through the rocky soil with a compression strenghth of 200 MPA.thi s type of cutting

wheel ,also used in soil containg large b;pcks,is not suitable for clayey soil .

• To ensure the stability of the face ,the contact pressure of the cutting wheel and the confing

pressure must be equal to the earth pressure and to the pore pressure of water if the boring

is done under the ground water table.thus the total pressure thus applied on the head must

be :-

- greater than the active pressure of the earth so as to avoid over excavation leading

to the settling on the surface or even subsidence .



- less than the passive earth pressure so as to avoid facing back the soil at the face

,leading to elevations of the surface or lateral movements likely to create disorder for

already –existing networks(Stein et al.,1994)

• In the case of hydraulic mucking ,this pressure is ensured by the slurry injected into the

chamber located at the back of the felling cone.it can be controlled more easily than the

pressure exerted by the soil mixed in the stpe of the scew type boring machines(Bennett et al

.1994).

Disposal of rubble (mucking)

There are three types:

• Hydraulic mucking – Removing the earth in suspension in a freely flowing fluid to the outside.

That fluid can be water or pressurised bentonite slurry.(See Figure 20)

• Mucking with a screw conveyor – The rubble is extracted from the stope using a spiral

conveyor (see Figure 20)

• Pneumatic mucking – This is a system that is rarely used and consist of mucking by suction

where the rubble is extracted from the face into an airtight vacuum container.

Figure 20: Principles of a hydraulic mucking boring machine (Herrenknecht documents)

Monitoring and correction of trajectory

• Controlling the actual trajectory of the boring machine in relation to its theoretical position ,is

done using a laser beam with the sensor located in the start shaft whose impact on a target

placed in the machine helps visualize the deviations in trajectory with the help of a camera on

board the boring machine

• When the deviation s become excessive it is possible to correct the direction of the machine

whose head is articulated by moving the three cylinders placed 120 c apart.

• 4-installation of pipelines by jacking.



• This is done by successive jacking of pipes behind the boring machine ,this pipejacking is

ensured by a thrust frame equipped with hydraulic cylinders and located in the starting shaft.

Pipes Materials

Many types of materials are used :-

• Concrete pipes represent the majority of pipelines that are currently laid .

• Pipes made of composite materials, known as “glass fibre reinforced plastic “offer very good

resistance to corrosion and thus are efficient in transporting corrosive fluids or for carrying

chemically aggressive soil, moreover they offer a high resistance at a lower weight the

external diameters available are between 400 and 2400 mm.

• Steel pipes have the major advantage of offering strong resistance but they are sensitive to

corrosion.

• Clay pipes available in diameters of 150 to 1200 mm offer greater resistance than the

concrete pipes at the same thickness .when their surface is vitrified ,it is extremely resistant

to water absorption and chemical attacks.

In terms of corrosion resistance the jacking pipes and their joints can be subject to internal corrosion

caused by the transported substances or to external corrosion caused by the surrounding soil or

ground water.

If the materials used are insufficient ly resistant ,measures of corrosion protection have to be taken

and approved by Dot.

For steel and ductile cast iron pipes the internal protection shall not be damaged during the jacking

process.

The methods vary in size, length and accuracy as shown in Table 4. Due to the limitations in

accuracy, non-steerable methods should only be used over short distances and where suThe soil

conditions and groundwater levels are of great importance in determining the most suitable method

for a given NDRC. In Table 2 a number of the common methods are shown with their respective

application in various soil types.

Some methods can be used in almost any soil conditions as long as the equipment and tools are

appropriate for the present soil types. Horizontal directional drilling (HDD) is an example, where drills

and reamers are available for nearly any soil type. HDD can however have limitations in coarse non-

cohesive soils where the cavity created by the reamer can have a tendency to collapse. This is



especially the case in very uniform soil particle size efficient clear distance to other utilities can be

guaranteed.

Table 4: NDRC methods with typical pipe size, length and accuracy

External pipe diameters, De

Maximum length

Accuracy Minimum ground cover

Non-steerable:

Impact moling/soil displacement hammer, Pipe ramming with closed pipe

Up to 200 mm 25 m 1-2 % of length 10 x De

Min. 3.0 m

Pipe ramming with open pipe, Auger boring

Up to 2000 mm 80 m 1-2 % of length 3.0 x De

Min. 3.0 m

Steerable:

Horizontal Directional Drilling (HDD)

40 - 1200 mm 1800 m 2-5 % of depth

Micro tunnelling 400-4500 mm 1000 m +/- 20 mm 3.0 x De Min. 3,0 m

Pilot pipe with auger spoil removal

100 - 1200 mm 100 m +/- 20 mm 3.0 x De Min. 3.0 m

Manned steerable:

Pipe jacking 1500 - 4500 mm

1000 m +/- 20 mm 3.0 x De Min. 3.0 m

Hand excavation:

Hand dig + Mechanical excavator

Min 1500mm 125m Varies 3.0 x De Min. 3.0 m

.

Micro tunnelling or pipe jacking with closed front can also be applied in nearly any soil condition with

the suitable bore heads and spoil removal systems. However, in very loose non-cohesive soils, with

high groundwater levels, there is a risk of removing excessive soil in front of the bore head, which

may lead to immediate or future surface settlement.

In very loose soils or areas where soil investigations have indicated subsurface cavities, a decision

must be made either to construct deeper in an attempt to find suitable soil conditions or to apply

ground treatment methods prior to undertaking the NDRC.

In Figure 2 a number of grout types are indicated for use as ground treatment methods.

The final selection of an NDRC system should be developed using available factual and reliable soil

data and surrounding constraints. The system should include the recommended route (line and

level), boring size, NDRC method, pipeline details, equipment, and operational variables, all of

which, in combination, will achieve the required tolerances. The proposed system should then be

analyzed for:

• Jacking/pulling forces.

• Lubricant characteristics.

• Face stability.



• Thrust reaction elements.

• Structural design of pipe and joints.

• Ground surface movement (both short and long term settlement and heave).

Please refer to the Tunnelling and Pipe Jacking Guidance for Designers table which is

shown in Appendix E

Drilling fluids

Functions

Generally, the fluids used for boring may have several essential Functions:

• maintaining the cutting in suspension and ensuring its removal by hydraulic channels: this

obviously is a function that is directly applicable to boring machines with hydraulic mucking;

• guaranteeing the stability of the bore, strengthening the walls and preventing loss of fluids by

creating an external or internal “cake” that is as fine and as resistant as possible. This is a

supporting function;

• lubricating and cooling the tools, drilling strings, on-board equipment and pipelines;

• facilitating digging by jetting. This function is sometimes necessary in clayey ground

• The drilling mud is essentially made up of a stable colloidal suspension in a Dispersing agent

like water. Two families of colloids are mainly used:

- Mineral: mainly bentonite,

- Organic: mainly water-soluble polymers.

• This suspension is rapidly altered by solids in the ground and possibly by water contained in

the ground to be crossed and the minerals contained in it.

• The bentonites are industrial clay of the smectite group. They are characterized by a foliated

structure, which is negatively charged on surfaces and positively on.

Main characteristics

Main characteristics parameters of drilling fluid, which determine its behavior and which must

be regularly measured and recorded as the digging work progresses:

• the density, which is an index of the content of solid element in the polluted sludge; it must

generally be between 1.0 and 1.2;

• the viscosity, which characterizes the ability of forming a cake as well as the ease in

transportation of the mucking; measured at the Marsch cone, it must generally be between

32 and 40 seconds in clayey ground, and greater than 50 seconds in sandy ground;

• the yield point, the thixotropy and the filtrate that determine the formation of the cake and its

ability to reform rather rapidly; in a filtration test, clean sludge must present a cake less than

4 mm and a filtrate less than 40 cm3; in polluted sludge the cake must remain less than 3

mm, and the filtrate must be in the region of 6 cm3 in clayey ground, and 10 to 15 cm3 in

sandy ground;

• the sand content, which results from the separation result of solid earth and which affects the

permeability of the cake and therefore its stability; it must generally remain less than 4 to 5 %

(measured with the elutriator); Guidelines for a Project Design 297



• the pH, which affects the ionic balance and thus the physico-chemical properties of the

sludge; it must remain within a range of 8 to 10;

• the conductivity and the hardness are also indices that may be useful.

NOTE: the values indicated above are only to indicate the order of magnitude generally used in

trenchless work. They must however be adjusted according to predominant performances, which are

dependent on the ground.

• Implementation of drilling fluids requires suitable manufacturing, storage and solid treatment

equipment:

- mixers,

- main and auxiliary pumps,

- mud tanks, vibrating screens, hydrocyclones, centrifuges, and possibly a plant for the

physico-chemical treatment of waste.

• The equipment as well as the quality of process water and the temperature will significantly

affect the performances of the sludge.

• On the other hand, it is very essential to emphasis that the storage conditions (long periods,

humid atmosphere, etc.) can significantly alter the characteristics of the bentonite powder.

• fractures. Upon contact with water, the flakes disperse, swell and possibly exchange the

charge compensating cations.

• Beyond a certain concentration (relatively low) of the order of 4 to 6%, and depending on the

quality of bentonite, a stable structure develops and has certain

• Rigidity under shearing.

• The bentonite can be combined with additives for various functions:

• Viscosifying, fluid-loss additive, water reducer, clay encapsulator and stabilizer,

• Lubricant.

• The most common are water-soluble polymers which, in addition to their ability In increasing

the viscosity, present special physico-chemical properties.

• There exist several types that are natural, artificial or synthetic, which can remedy

specific problems relating to certain soil materials, such as:

- Sticky or swelling clay,

- Improvement in the stability in sand and gravel,

- Better resistance to physical or chemical contaminations,

- Abrasiveness.

4.3.1.2 HDD process All types of horizontal drilling have the following common functions:

Drilling of a pilot tube

• A drill string is inserted into the ground applying on the bottom hole assembly a combined

thrust and rotation action. This bottom hole assembly has a special feature of being

asymmetrical in relation to the longitudinal axis. Mere thrust forces it to deviate, but rotation

combined with the thrust gives it a straight trajectory.



• This bottom hole assembly consists of an electronic tracking device and more or less

sophisticated cutting tools. These tools are either simple drill blades or drill bits driven by

hydraulic or pneumatic motors.

Monitoring and correcting the trajectory

The installation of pipelines by horizontal drilling must be able to:

• constantly locate the position of the drilling head in the ground so as to respect the specified

trajectory and avoid the already existing utilities: this is the tracking function;

• know the pitch of this head and its direction to guide and divert its trajectory: this is the

guidance function.

It is in fact the asymmetry of the head (wearing blade and nozzles in the case of a conventional head

or a bend in the case of a mud motor) which by stopping the rotations of the rods diverts the

trajectory, thereby correcting it.

The success of pilot drilling depends on the locating system, its accuracy and ease of use.

Two types of locating systems may be distinguished:

• Walk-over systems

• These systems are suitable at most sites.

• This technique is easy to implement, is safe for data transmission cables and has a low

investment cost.

• The walk-over systems have disadvantages such as the reduction in accuracy of

measurements increasing with the drilling depth, the influence of underground magnetic field

interference and an operating range dependent on the life of the transmitter’s batteries.

• Down hole systems or wire line steering systems

The systems consist of three elements:

• a transmission probe powered by batteries placed in the drilling head,

• a receiver that helps vertically locate the head and its direction,

• display of parameters (remote) on the drill rig.

Figure 21: Locating systems



Reaming of the drilled borehole

• Once the pilot hole has been made, the drill string comes out of the exit pit (most frequent

case).

• Generally, the drill string is towed behind the reamer. The hole is enlarged by successive

stages of reaming of increasing sections until the desired section is reached (generally

double the section required by the pipeline).

• This reamer is equipped with injection jets for drilling “mud”. This mud washes out and

disposes of the cuttings created by the reamer, lubricates and cools the cutting tools and

strengthens the borehole.

• After the final reaming phase one end of the pipeline built earlier will be tied to the pulling

head fastened to a suitable reamer. It will be pulled from one drilling end to the drill rig.

Installation of pipes or cables

Used to cross obstacles such as streams or rivers, this guidance technique using data transmission

cables has opposite advantages and disadvantages to the previous system with a more complex

usage technique but with greater accuracy and range.

The horizontal directional drilling system

The horizontal directional drilling system include:-

• Drill unit.

• Guidance system.

• Drilling fluid system.

• Drill pipe and down hole tools, including bits and back reamers.

• Drilling fluid mixing or recycling system.

Figure 22: Basic components of rig



HDD systems are defined by:

• Thrust and pullback force, stated in pounds

• Spindle torque, stated in foot pounds

• Maximum volume of drilling fluid a machine can pump per minute, and spindle

• Revolutions per minute.

Table 5: Rigs types and specification

• The composition of drilling fluid and correct/constant pressure are keys in successful

installation of HDDs.

• Too low pressure may cause collapse of the bore cavity or clogging of soil removal. Too high

pressure may result in blow out, where drilling fluid is pressed through overlying soils to the

surface.

• Horizontal directional drilling can be undertaken in both soil and rock, and there are no

specific limitations under ground water. Some restrictions may apply in very loose coarse

sand or gravel. These soils will have a tendency to collapse in the borehole giving either

excessive spoil removal or stopping the pipeline.

• Pipe materials are most often plastic (PE, PP or PVC), but steel and cast iron pipes are also

manufactured for use in HDD installations. Pipe materials must be joined and have the

strength necessary to withstand the pulling forces applied during installation.

• The accuracy of HDD is dependent on the accuracy of which the drill heads location and

depth can be determined during drilling. Accuracy has typically been set at 2-5% of the

depth, but more accurate transmitting/receiving equipment is continually being developed.

Drill Bits

• The latest bit designs are for specific types of soils, including rock, cobble, and other difficult

conditions. Carbide makes today’s bits more productive and last longer.

• Bits are designed to run smoother in difficult conditions, with less vibration transmitted to the

drill unit.

• A truly universal bit that is effective in all soils has yet to be developed, but some of the latest

bits can be productive in a much wider range of soils.



• For much of today’s short- to medium-range utility applications, slant-face bits also make it

possible to change the direction of the path of the pilot bore.

• Many new bit products are for rock work, and drilling and steering through hard rock remain a

challenge for both tool and drill-rig designers.

• Some drill bits are used for steering and to excavate the soil or rock at the face of the bore.

• The types of drill bits commonly used in HDD applications are traditional Slanted-face bits,

slanted-face rock bits, and hard rock or mud motor bits.

Table 6 provides some application guidelines for the various types of drill bits.

Table 6: Drill Bit Types and Application Guidelines (Courtesy DCCA)



Figure 23: Slanted face Drill Bits

Figure 24: Modified Slanted face Drill Bits



Figure 25: Modified Slanted face Drill Bits

Figure 26: Rock Drill Bits



Figure 27: Tri-Cone Rock Bits

Guidelines on EHS and risks for HDD

The constraints linked to the safety and protection of the environment must be considered in the

study. All DoT and international rules must be followed during the work. The elements mentioned

below Figure only as additional elements and can on no account substitute the current rules.

Before starting the work, it is necessary for all personnel present at the site to attend an information

meeting on accident and their prevention, means of rescue and emergency organizations.

Taking adequate steps may prevent the following hazards linked to horizontal drilling:

Work on inclines

The working area used on the machines must be of non-skid material and be easy to clean. Fixed

handrails must prevent the risk of falls.

Work on rotating mechanical parts and tools

Contact with rotating mechanical parts must be prevented in every possible way by fixed safety

installations. The working clothes of the personnel operating the machines must be tight fitting and

closed. During the rotation of the drilling rods, a clearance distance must be maintained.

Risk of slipping increased by the presence of drilling mud

During the dismantling of the drilling rods, the bentonite mixtures must be collected in salvage tanks.

Clean water must be available for the cleaning of the work area near the machines and mixer

Respiratory risks related to the inhalation of bentonite powder

Suitable techniques to avoid working as much as possible in areas subject to contamination by

bentonite powder must be employed. Work in these areas must be done only by those wearing anti-

dust masks (half-masks that filter particles) and airtight protective eyewear.



Handling of loads during lifting

The handling of drilling rods and other loads by lifting appliances must be done with great care. The

proper condition of pipe tongs, slings and straps must be frequently monitored. Staying under

suspended loads must be strictly avoided. In all cases, it is necessary to maintain a safe distance

from overhead lines of any type.

Significant torsional moments during the tightening or loosening of drilling rod/tool unions

Special attention must be paid to the proper working condition of tightening and cutting tools. In

particular, spring collets must be used with great care and only by skilled personnel. Special

attention must also be paid to the proper condition and safety of the workstation at the drilling exit

point.

Communication between the control cab, the drilling rig and the pipeline side

To eliminate the dangers created by the drilling rig at the exit point by rotating tools, it is necessary to

ensure continuous radio communication. With no visual contact between the machine and the

pipeline sides, the use of a receiver-transmitter headset as well as walkie-talkies is recommended. In

all cases, it is necessary for the operator of the drilling machine and the person in charge of the

pipeline side to coordinate themselves before starting the work.

Work under thoroughfares

The risks are not limited to horizontal drilling except for the operator who “follows” the pilot hole with

the receiver. Engrossed in using the receiver, he may not always be aware of his safety. It may be

necessary to protect his route and/or stop the traffic temporarily while crossing the road.

Risks of aggressions on underground structures

The risk of sometimes coming into contact with high voltage electrical transmission lines requires a

rigorous use of the drilling machine and insulation of the personnel. In the case of a damaged gas

pipeline, all ignition sources must be removed: the machine and all the equipment near the leak must

be stopped, as well as all electrical devices (including mobile phones). When gas pipelines are

present in the drilling area, the site manager must provide the co-ordinates of the concerned gas

company.

Security of machines

The machines used for carrying out horizontal drilling projects must meet the European

recommendations as well as the national regulations applicable to them. A compliance statement as

well as the issuing of the CE acronym linked to it must be provided by the manufacturers of different

machines. Independent monitoring of the machines is possible. It will be done by the competent

national authorities as far as safety is concerned. This is linked to the qualification and for European

Tested. For protection against electrical accidents, the machines operating on electricity must be

properly earthed before use. The maintenance of complex hydraulic systems of horizontal drilling

machines must be done with care. The watertightness of these systems must be constantly

monitored.



Security of drilling tools

For drilling rods, tools, equipment, joints, reamers and links to be inserted inside the drilling, it will be

necessary to undertake a safety check by a qualified body in MQ or by a qualified or state

recognized monitoring institution (independent monitoring).

This monitoring must show that the drilling rods and the tools used inside the drilling are made of

suitable material. It must also show that the maximum stresses to tension, compression, torsion and

internal pressure incurred by the drilling machine used do not exceed 0.8 times the elastic limit of the

material (S = 1.25) according to the DIN, API bases and DS standard. For tools having rotating parts

such as downhole mud motors, tricone bits or universal joints, one must ensure before every use

that a detailed and documented inspection is carried out. This will guarantee that they can be used

safely and without any restrictions (internal inspection).

Operational risks in HDD installations

Many risks will be associated with the HDD operations. Table 7 lists those risks must be assessed

within any method of statement will be submitted to DoT to get approval for HDD operation.



Table 7: Operational risks in HDD installations (Baumert and Allouche 2003)

NO

N D

ISR

UP

TIV

E R

OA

D C

RO

SS

ING

S M

AN

UA

L

P

age 5

5

January

2013

Figure 28: Experience guidelines for the application of different NDRC methods

Soil classification

Rock

Non-cohesive

Inter-bedding

Cohesive

Method

Dense

Medium dense

Loose

Very

stiff

Firm to

stiff

Very soft to

soft

Non-steerable methods:

With soil displacement

With soil removal

Steerable:

Directional drilling

Micro tunnelling

Pilot pipe jacking with soil removal, over

GW

Pilot pipe jacking with soil removal, under

GW

Manned steerable techniques:

Pipe jacking with open face, over GW

Pipe jacking with open face, under GW

Pipe jacking with closed face

Ground Treatm

ent:

Cementitious grouts

Suspension grouts - clay filler grouts

Low viscosity grouts - resins

Chemical grouts - silicates

GW = Ground water

Ma

in

are

a

of

ap

plica

tio

n

A

pp

lica

tio

n

po

ssib

le

A

pp

lica

tio

n

crit

ica

l

Notes:



4.3.1.3 Working shafts, entry and exit points Launch and reception shafts shall be designed and constructed to withstand all applicable

static and dynamic loads including the maximum driving force that may be applied. The

location of launch and reception shafts shall be selected to ensure safe working distances to

roads, buildings and other structures (see Table 8).

Figure 29: Working shafts

Table 8: Design of working shafts in Dry ground



Table 9: Design of working shafts in wet ground

For DOT Main Roads, a minimum distance of 5.0 m from any shaft to the edge of the

embankment shall be ensured. For Municipality roads in cities or towns, this distance may

be difficult to achieve due to buildings and other structures. If 5.0m cannot be achieved, then

Consultant/Contractor shall present the reasons and the methods proposed to protect the

asset affected by the crossing. Special care must therefore be taken in the placement,

excavation and backfilling of shafts to avoid any damage. Slope stability must be examined

and taken into account when submitting solutions to the DoT.

For horizontal directional drilling (HDD) the entry and exit points should be at a sufficient

distance to ensure the acceptable radius of the drilling equipment and piping material.



Table 10: Shaft Dimensions

The dimensions of launch and reception shafts shall be kept to a minimum necessary to

construct the NDRC. Examples of shaft sizes for pipe jacking or micro tunnelling are shown

in Table 11.

Table 11: Shaft sizes

DN External Pipe

Diameters (mm) Segment lengths

Dimensions of launch shaft

Dimensions of reception shaft

200 - 300 Up to 406 1.0 m 2.0 m diameter or 2.5 m x 2.0 m

2.0 m diameter or 2.0 m x 2.0 m

400 - 800 556 - 970 2.0 m 3.2 m diameter

or 4.5 m x 3.0 m 2.6 m diameter or 3.0 m x 2.5 m

800 - 1400 1100 - 1720 3.0 m 5.8 m x 4.0 m

or 6.0 m diameter 4.5 m x (2.5-3.0 m)

1500 - 3000 1820 - 3600 3,5 m 10.0 m x (4.5-6.0 m) or 10.0 m diameter

6.0 m x (3.0-4.6 m)

Shafts beneath the water table shall be water tight and the base concrete shall be capable of

withstanding external uplift pressure of groundwater in addition to other loads.

Entry and exit seals or ground treatment of the soil outside the shaft will be required to

ensure that there is no soil transport into the shaft when initiating the drive.

When deciding entry and exit points, it is important to allow for a safe soil cover throughout

the crossing length under the road.

4.3.2 Design drawings Drawings required for approval of the preliminary design include:-

• Map of location

• Plan and profile showing the line, level and diameter

• Plans of existing utilities, buildings and structures

• Geotechnical profile along the drive line (showing ground water elevations)

• Plan of working areas showing approximate size and location of shafts, entry or exit

sties



4.3.3 Hand excavation If hand excavation is considered appropriate (when no other option is available), then this

must be planned very carefully in line with the specific Health and Safety requirements of the

project. The most appropriate tools must be used and all personnel must be adequately

trained to work in confined spaces. Please refer to the Tunnelling and Pipe Jacking

Guidance for Designers table which is shown in Appendix E and e consult the EHS Manual

for further details.

4.4 Pre-construction stage Prior to commencing construction the final design of the proposed NDRC must be completed

and approved by all relevant authorities. This is often undertaken by the specialist Sub-

contractor, who has the experience and the detailed information about the method and

equipment to be used.

All calculations, drawings, method statement, etc. must however be approved by the

Client/Consultant before submitting to the Road Authority for construction approval.

4.4.1 Design calculations Design calculations shall include:-

• Calculations for any thrust and receptions pits/shafts which shall be designed to

resist external soil and water pressure and stresses resulting from the jacking

machine.

• Pipe calculations showing capability of pipe to resist jacking and friction forces in the

axial direction along with soil, ground water and traffic loadings in the vertical

direction.

• Calculations of friction loads, face loads, interjacks, jacking pressures etc. for the

complete system including thrust walls, which demonstrate how pipes will be installed

with no damage.



• Calculations giving predicted settlements along and adjacent to route of pipeline.

• Calculations supporting maximum jacking capacity with appropriate factor or safety.

4.4.2 Design drawings Drawings must include:-

• Comprehensive plan, profile, and section drawings of the proposed drive showing all

necessary details (such as internal and external diameter, wall thickness, joints or

connections)

• Working drawings showing on plan and section the method of supporting excavations

(Temporary Works).

• Drawings showing the location of pits/shafts

including those indicated as permanent

works in the design drawings.

• Foot print plans showing the working site

areas at the thrust and reception pits/shafts,

control room, pipe storage area, craneage

area, slurry tank, generator, etc.

• Plans showing proposed traffic and

pedestrian diversion proposals around all

pits/shafts.

• Details of entry and exit pipe seals and seal rings in pits/shafts.

• Jacking and receiving pit configurations (plus design and construction details)

• Ground support details

• Any relevant requirements for thrust blocks, backstops etc

• Site logistics including storage areas, excavation and backfilling procedures etc

• Plans for de-watering

• Settlement Monitoring Plan, including monitoring points, benchmarks, and survey

procedures.

• Jacking and receiving pit working drawings, including configuration, support, storage

details etc.

4.4.3 Ground Surface Movement The goal of any NDRC undertaking should be to avoid ground surface movement entirely.

Unacceptable ground surface movement (settlement or heave) shall be defined as

movement greater than 6.0 millimetres vertically anywhere in the centreline of the NDRC

drive or adjacent surfaces and structures. Some important considerations include:

• During pipe jacking, ground movement may occur due to the instability of the face of

the bore, or from the elastic unloading of ground caused by excavation. These may

be referred to as short term settlement and heave.

• Providing good practice is followed, the effect of such movements should not be

adverse.

• Long term movements may occur due to closing of the overbreak.

• Pipe jacking has the advantage that the overbreak is minimal and may be

pressurised in certain soil conditions.



• The combination of NDRC drive methods and pipeline details are the key to

preventing excessive surface movement, which may be related to:

- Diameter and depth of drive.

- Boring method and practice.

- Stiffness of pipe and joint system and structural integrity.

- Joint alignment.

- Maximum jacking/pulling forces.

- Lubrication and flush details.

- Pipe/soil interaction.

- Overcut and its management.

- Face support details.

- Groundwater control details

- Lack of post-installation annular injection

- Over-cutting in layers with consistency differences

- Inadequate rate of advancement

• Obstruction collisionRegardless of drive method or details, surrounding soil may be

susceptible to excessive movements when disturbed by the drive (bore). The

following conditions can influence ground movements:

- Residual or swell stresses leading to radial-elastic or time-dependent

movements.

- Weak soils or shear failure of the face.

- Loose compressible soils around or above the drive leading to densification

and hence ground movement upon disturbance.

- Internal erosion of loose, non-cohesive soil due to uncontrolled groundwater

movements.

- Loss of soil mass due to dissolution of salts by moving water through soils

with high salt content

4.4.3.1 Prediction of ground surface movement Theoretical procedures, combined with empirical correlations may be used to assess

potential ground movement above the tunnel. Since tolerances against ground surface

movements are small, the Department recommends that worst credible design assumptions

and methods be used in the assessment and that total, not fractional, movements be

determined.

For initial assessments, and where ground settlement effects are not critical, traditional

settlement calculations based on an estimated volume loss during tunnelling may be

sufficient.

Standard empirical analyses such as those presented by) should always be undertaken

where the effects of ground settlement due to tunnelling are an issue. Simple methods of

calculating the extent and potential shape of the settlement trough laterally to, and axially

along, the tunnel are given in numerous text books and guidance documents (i.e. CIRIA

Project Report No. 30 1997).



O'Reilly and New (1983) presented the following formula for determining the maximum initial

settlement above the tunnel axis as:

,

or

Smax = 0.025.Vl(r2/z0)

Where:

VL is the total volume loss of ground per unit advance in m3,

Vl is the volume loss as a percentage of the tunnel volume,

r = pipeline radius,

z0 is depth to centre of pipeline and

i is a coefficient related to the width of the settlement trough:

When tunnelling through granular deposits such as sand however, account needs to be

taken of the modified shape of the settlement trough. Jacobsz, Sanding et al suggest that

the profile of the settlement trough in sands is better predicted by the formula:

S = Sm.exp[-1/3.(x/i)1.5]

Rather than the usual formula:

S = Smax.exp (-x2/2i2)



based on the Gaussian distribution normally adopted.

S = ground settlement at point x transverse to the tunnel axis

Smax = maximum calculated settlement

i = distance from tunnel centre line to point of inflection of the settlement trough.

Determinations of potential damage to all structures located within the settlement trough

should be carried out as described in the CIRIA documents PR 30 and SP 201 and

elsewhere.

Another method can be used

4.4.3.2 Analysis of subsidence trough The analysis of subsidence trough consists of several sequential steps:

• Determination of the maximum settlement and dimensions of subsidence trough for

individual excavations

• back calculation of the shape and dimensions of subsidence trough providing it is

calculated at a given depth below the terrain surface.

• determination of the overall shape of subsidence trough for more excavations

post-processing of other variables (horizontal deformation, slope)

• The analysis of maximum settlement and dimensions of subsidence trough can be

carried out using either the theory of volume loss or the classical theories (Peck,

Fazekas, Limanov).

4.4.3.3 Volume loss The volume loss method is a semi-empirical method based partially on theoretical grounds.

The method introduces, although indirectly, the basic parameters of excavation into the

analysis (these include mechanical parameters of a medium, technological effects of

excavation, excavation lining etc) using 2 comprehensive parameters (coefficient k for

determination of inflection point and a percentage of volume loss VL). These parameters

uniquely define the shape of subsidence trough and are determined empirically from years of

experience.



Settlement expressed in terms volumes

The maximum settlement Smax, and location of inflection point Linf are provided by the

following expressions:

where:

A - excavation area

Z - depth of center point of excavation

k - coefficient to calculate inflection point (material constant)

VL - percentage of volume loss

The roof deformation ua follows from:

where:

r - excavation radius

VL - percentage of volume loss

Recommended values of parameters for volume loss analysis:-

• Data needed for the determination of subsidence trough using the volume loss

method:

• Coefficient to calculate inflection point k

Soil or rock k



• Coefficient to calculate inflection point k

Soil or rock k

cohesion less soil 0,3

normally consolidated clay 0,5

over consolidated clay 0,6-0,7

clay slate 0,6-0,8

quartzite 0,8-0,9

• Percentage of volume loss VL

Technology VL

TBM 0,5-1

Sequential excavation method 0,8-1,5

• Several relationships were also derived to determine the value of lost volume VL

based on stability ratio N defined by Broms and Bennermarkem:-

where:

σv - overall stress along excavation axis

σt - excavation lining resistance (if lining is installed)

Sn - undrained stiffness of clay

• For N < 2 the soil/rock in the vicinity of excavation is assumed elastic and stable. For

N ∈ < 2,4 local plastic zones begin to develop in the vicinity of excavation, for N ∈ <

4,6 a large plastic zone develops around excavation and for N = 6 the loss of stability

of tunnel face occurs. Figure 30 shows the dependence of stability ration and lost

volume VL.



Figure 30: Stability Vs Volume Loss

• Ground settlement is of greater concern for soft ground tunnels than for rock for two

reasons:

• Settlements are nearly always greater for soft ground tunnels.

• Typically more facilities that might be negatively impacted by settlements exist near

soft ground tunnels than near rock tunnels.

• With modern means and methods, both the designer and the contractor are now

better equipped to minimize settlements and, hence, their impact on other facilities.

Sources of Settlement

Although there are a large number of sources or causes of settlement, they can be

conveniently lumped into two broad categories: those caused by ground water depression

and those caused by lost ground.

Groundwater Depression Groundwater depression may be caused by intentional lowering of

the water during construction or by the tunnel itself (or other construction) acting as a drain.

When either of these occurs the effective stress in the ground increases. Basic soils

mechanics can then be applied to estimate the resulting settlement. For tunnels in granular

soil the settlement due to this increase in effective stress is usually reflected as an elastic

phenomenon requiring knowledge of the low stress modulus of the ground and calculation of

the change in effective stress. Unless the soil contains silt or very fine sand, this elastic

settlement will typically represent the majority of the total but its absolute value will also be

relatively small.

For fine grained soils, the situation is a bit more challenging but certainly manageable using

normal soil mechanics approaches. With fine-grained soils, the conditions are reversed. In

most instances, the settlement is mostly due to consolidation brought on by the changes in

effective stress and hence is analysed by the usual soil mechanics consolidation theories. In

some instances, primarily if lenses of sands are contained in the soil, there may also be a

relatively small contribution by elastic compression. In comparison to the settlement of



granular soils, consolidation can lead to several inches of settlement when the consolidating

soils are thick and the change in effective stress is significant.

Lost Ground Lost ground has a number of root causes (at least nine) and is usually

responsible for the settlements that make the headlines. By definition, lost ground refers to

the act of taking (or losing) more ground into the tunneling operation than is represented by

the volume of the tunnel. Thus it is highly reflective of construction means and methods. As

will be discussed, modern machines can be a great help in controlling lost ground but in the

end it usually comes down to quality of workmanship.

For the purposes of this manual, the causes of lost ground are lumped into three groups:

face losses, shield losses and tail losses.

Face losses results from movement in front of and into the shield. This includes running,

flowing, caving, and/or squeezing behavior of the ground itself or simply mining more ground

than displaced by the tunneling machine.

Shield losses occur between the cutting edge and the tail of the shield. All shields employ

some degree of overcut so that they can be maneuvered. In addition, any time a shield is off

alignment, the shield yaws, pitches, or plows when brought back to alignment. Mother

Nature abhors a vacuum and the surrounding soils begin to fill these planned or produced

voids the instant they are produced. Note that a one inch overcut plus one-eighth inch hard

facing on a 20 foot shield produces lost ground of nearly two percent if not properly filled

[1.125/12 (20) 3.1416 ]/ (10)2 3.1416 = 1.88%).

Tail losses are similar to shield losses in that they are caused by the space being vacated by

the tail itself as well as the extra space that must be provided between the tail and the

support elements so those elements can be erected and so that they don't become "iron

bound" and seize the tail shield. However, like the shield losses, these tail voids will rapidly

fill with soil if they are not first eliminated by grouting and/or expansion of the tunnel support

elements.

Estimates of settlement in soft ground tunneling are just that, estimates. The vagaries of

nature and of construction are such that settlements cannot be estimated in soft ground

tunnels to the same level of confidence as, say, the settlement of a loaded beam. In

tunneling we rely heavily on our experience with some assistance from analysis. Thus, there

are two related methods to attack the problem: experience and empirical data.

Experience can be used where a history of tunneling and of taking measurements exists. An

example of this where soft ground tunnels have been constructed in well-defined geology for

over 40 years. During that time the industry has progressed from basic Brunel shields to the

most current closed-face tunneling machines. For this case it would be anticipated that an

experienced contractor would achieve between 0.5 and 1.0 percent ground loss (see Table

12 ). An inexperienced contractor would attain 1.0 to 2.0 percent loss.



Table 12: Relationship between Volumes Loss and Construction Practice and Ground Conditions

Case VL (%)

Good practice in firm ground; tight control of face pressure within closed face machine in slowly raveling or squeezing ground

0.5

Usual practice with closed face machine in slowly raveling or squeezing ground

1.0

Poor practice with closed face in raveling ground 2

Poor practice with closed face machine in poor (fast raveling) ground

3

Poor practice with little face control in running ground 4.0 or more

When there is no record to rely upon, the design would have to be based strictly on empirical

data and an engineering assessment of what the contractor could be expected to achieve

with no track record to rely upon. In that case the above evaluations might be bumped up

one-half percentage point each as an insurance measure

State-of-the-art pressurized-face tunnel boring machines (TBM) such as EPB and minimize

the magnitude of ground losses. These machines control face stability by applying active

pressure to the tunnel face, minimizing the amount of overcut, and utilizing automatic tail

void grouting to reduce shield losses. Typically, ground loss during soft ground tunnel

excavation using this technology limits ground loss to 1.0 percent or less assuming excellent

tunnelling practice (adequate pressure applied to the face and effective and timely tail void

grouting).

The volume of ground loss experienced during tunnelling can be related to the volume of

settlement expected at the ground surface (Peck, 1969). For a single tunnel in soft ground

conditions, it is typically assumed the volume of surface settlement is equal to the volume of

lost ground. However, the relationship between volume of lost ground and volume of surface

settlement is complex. Volume change due to bulking or compression is typically not

estimated or included in the calculations. Ground loss will produce a settlement trough at the

ground surface where it can potentially impact the settlement behaviour of any overlying or

adjacent bridge foundations, building structures, or buried utilities transverse or parallel to

the alignment of the proposed tunnel excavation. Empirical data suggests the shape of the

settlement trough typically approximates the shape of an inverse Gaussian curve (Figure

31).

The shape and magnitude of the settlement trough is a function of excavation techniques,

tunnel depth, tunnel diameter, and soil conditions. In the case of parallel adjacent tunnels,

surface settlement is generally assumed to be additive. The shape of the curve can be

expressed by the following mathematical relationships (Schmidt, 1974).



Where:

w = Settlement, x is distance from tunnel or pipeline centerline

i = Distance to point of inflection on the settlement trough

The settlement trough distance, i is defined as:

i = KZΟ

Where:

K = Settlement trough parameter (function of soil type)

ZΟ = The depth from ground surface to tunnel springline

The maximum settlement, wmax is defined as:

Where:

VL = Volume of ground loss during excavation of tunnel

D = A diameter of tunnel.

Table 13 summarizes likely volumes of lost ground as a percentage of the excavated volume

and a function of combined construction practice and ground conditions.



Figure 31: Typical Settlement Profile for a Soft Ground Tunneling

For geometrics other than a single tunnel, adjustments of the types given below should be

made to obtain settlement estimates:

For parallel tunnels three or more diameters apart (center to center), surface settlements are

usually reasonably well predicted by adding the individual bell curves of the two tunnels. In

good ground and with good practice, this will often give workable approximations up to the

point where the tunnels are two diameters apart. On the other extreme, when the tunnels are

less than one and one-half diameters apart, the volume of lost ground assumed for the

second tunnel should be increased approximately one level in severity in Table 13 before the

bell curves are added. Intermediate conditions may be estimated by interpolation.

For over-and-under tunnels, it is usually recommended that the lower tunnel be driven first

so that it does not undermine the upper tunnel. However, driving the lower tunnel will disturb

the ground conditions for the upper. This effect may be approximated by increasing the lost

ground severity of the second (upper) tunnel by approximately one level in Table 13 before

adding the resulting two settlement estimates to approximate the total at the surface.

(Monsees, 1996)

As shown in Figure 31 the width of the settlement trough is measured by an i value, which is

theoretically the horizontal distance from the location of maximum settlement to the point of

inflection of the settlement curve. The maximum value of the surface settlement is

theoretically equal to the volume of surface settlement divided by 2.5 i. Figure 32 illustrates

assumptions for i values (over tunnel radius R) for calculating settlement trough width in

various ground conditions.



Figure 32: Assumptions for width of settlement trough (adapted from Peck, 1969)

The ground settlement also can be predicted by numerical methods. The numerical method

is extremely useful when the tunnel geometry is not a circular or horse-shoe shape since

analytical/empirical method is not directly applicable. A sample finite ement settlement

analysis is shown in Figure 33.



Figure 33: Example of Finite Element Settlement Analysis for Twin Circular Tunnels under Pile Foundations

Evaluation of Structure Tolerance to Settlement

Evaluation of structural tolerance to settlement requires definition of the possible damage

that a structure might experience. Boscardin and Cording (1989) introduced three damage

definitions for surface structures due to tunnelling induced settlement (where settlement is

calculated per Section 7.5):

• Architectural Damage: Damage affecting the appearance but not the function of

structures, usually related to cracks or separations in panel walls, floors, and finishes.

Cracks in plaster walls greater than 1/64-in. wide and cracks in masonry or rough

concrete walls greater than 1/32-in. wide are representative of a threshold where

damage is noticed and reported by building occupants.

• Functional Damage: Damage affecting the use of the structure, or safety to its

occupants, usually related to jammed doors and windows, cracking and falling

plaster, tilting of walls and floors, and other damage that would require nonstructural

repair to return the building to its full service capacity.

• Structural Damage: Damage affecting the stability of the structure, usually related to

cracks or distortions in primary support elements such as beams, columns, and load-

bearing walls.

Where determination of the surface settlement trough is critical, for instance where

settlement sensitive structures are located within the settlement trough, more sophisticated

methods of modelling should be used, such as finite element or finite difference numerical

models. In some cases, 3D numerical modelling techniques may be appropriate. Where

numerical modelling is adopted, use of small-strain stiffness’s can be used if appropriate.

However it should be noted that numerical models using small strain stiffness’s often



overestimate the width of the settlement trough which can lead to an under prediction of the

settlement and the associated curvature of the trough profile.

Settlement analysis, whether using empirical formulae or numerical modelling should

consider the effects of all elements affecting the settlement and settlement profile, which

may include, but may not be limited to:

• Elastic, elastoplastic, and viscoplastic deformational behaviour.

• Immediate, short-term, and long-term movements.

• Consolidation, collapse, and swell.

• Volumetric compression and expansion.

• Volume loss, soil piping, internal erosion, and hydro-compaction.

• Fractional and total ground movements

• Surface conditions including surcharge and topography

• Groundwater conditions, temporary and permanent including the effects of

dewatering.

• 3D effects

A discussion of some of the various elements influencing settlement and damage relating to

tunnelling can be found in CIRIA Special Publication SP 201 (2003)

For purposes of monitoring ground surface movement on the roadway, the Contractor shall

install flush-head pins (35.0 millimetres to 50.0 millimetres in length) in the road pavement.

The pins shall be installed in a grid pattern at approximately 2.0m centres.

The location of monitoring points and reference benchmarks are to be submitted before

approval to construct can be provided.

The grid of monitoring points shall cover the entire width of the roadway along the drive and

shall extend outwards in each direction from the centreline of the drive to a distance of the

drive centreline depth below the road surface.

Measurements shall be replicable to a level of 0.5 mm and shall be done on a daily basis

during construction. Ground surface movement outside the acceptable limit shall be

immediately reported to the Road Authority and remedial actions taken. Ground surface

movement limits in the specified area shall remain in effect for 2 years from date of

completion of the NDRC and shall be monitored on a monthly basis.

All surface monitoring shall be referenced back to stable benchmarks located well away from

the influence of the tunnelling works. If no existing permanent stable benchmarks are

available within 500m of the tunnel centreline, then a temporary deep benchmark shall be

installed.

Depending on the requirements of the design, additional monitoring may be required. Such

monitoring may include but may not be limited to the following:

• Vertical and/or horizontal inclinometers

• Vertical and/or horizontal borehole extensometers



• Movement monitoring pins attached to sensitive structures

• Standpipe, pneumatic and/or vibrating wire piezometers

• Strain gauges

• Electrolevels

• Portable seismographs

A construction monitoring report shall be prepared prior to start of construction works, setting

out the methods of monitoring to be used. The report shall detail:

• Types and locations of all monitoring instruments

• Method of monitoring, including details of measuring and recording equipment,

calibration certificates and frequency of calibration etc.

• Frequency of monitoring including:-

- Frequency and period of baseline monitoring prior to tunnelling works

- Frequency of monitoring for each instrument during tunnelling works

- Frequency and period of monitoring for each instrument after completion of

tunnelling works

• Trigger levels for each instrument, to include

- Alert levels (when readings reach 80% of the expected design values)

- Action levels (when readings reach 105% of the expected design values).

- Alarm values (when readings reach or exceed values beyond the design

values and deemed to be excessive). Alarm values shall be determined on a

case by case basis for each instrument.

• A detailed action plan describing the procedures to be adopted at each trigger level.

4.4.3.4 Railways Special considerations may apply when crossing under or nearby railways. The railway

authority must be consulted for further specifications or requirements. The requirements are

not therefore available because it is under preparation till that time, the following are

proposed guidelines from the international practice used in USA.(9).

All utility crossings railroad trackage should have a minimum depth of cover of three (3) feet

below the flow line of the ditch or ground surface and five and one-half (5-1/2) feet from base

of rail. In fill sections, the natural ground line at the toe of slope will be considered as ditch

grade.

For all boring and jacking installations under main and passing tracks, greater than 26

inches in diameter, and at a depth of between 5.5 and 10.0 feet below top of tie, a

geotechnical study will need to be performed to determine the presence of granular material

and/or high water table elevation.

The use of plastic carrier pipe for sewer, water, natural gas and other liquids is acceptable

under specific circumstances. The use of plastic pipe is satisfactory if the pipe is designed to

meet all applicable federal and state codes, and if the carrier pipe is properly encased within



a steel casing pipe. This casing must extend the full width of the right of way. Casing may

be omitted only for gaseous products if the carrier pipe is steel and is placed ten (10) feet

minimum below the base of rail .

If the minimum depth is not attainable because of existing utilities, water table, ordinances,

or similar reasons, the line shall be rerouted.

Locations that are considered unsuitable or undesirable are to be avoided. These include

deep cuts and in wet or rocky terrain or where it will be difficult to obtain minimum depth.

Underground installations may be made by open-trenching from the property line to the toe

of the fill slope in fill sections and to the toe of the shoulder slope in cut sections but to no

closer than thirty (30) feet of the centerline of track. The remainder will be tunnelled,

augured, jacked or directional-bored through the roadbed. Refer to the following sections for

required encasement of utilities and boring requirements.

Manholes should be located outside railroad property, when possible. No manhole will be

located in the shoulder, shoulder slope, ditch or back slope, or within twenty-five (25) feet of

the centreline of track, and shall not protrude above the surrounding ground..

Jacking/boring pits shall be located a minimum of thirty (30) feet from the centreline of track,

and kept to the minimum size necessary.

Under-track bores shall be located greater than 150 feet from the nearest,Track switch or

other major structure.

4.4.3.5 Buildings/ Sensitive Structures All NDRC works shall hold a minimum clear distance of 5.0 m to any buildings, foundations,

bridges, retaining walls or other sensitive structures.

No NDRC work shall pass under bridges or retaining walls. If 5.0m cannot be achieved,

then Consultant/Contractor shall present the reasons and the methods proposed to protect

the asset affected by the crossing.

Generally, when dealing with adjacent structures, a full structural assessment must be

produced to establish the potential impact of the crossing.

Precautions that can be adopted to prevent, control or minimise settlement of overlying

structures include:

Development of accurate baseline conditions

A good understanding of the geology to be tunnelled is key to predicting and avoiding or

controlling settlements due to tunnelling. Proper and sufficient site investigation is key to

developing appropriate mitigation methods for controlling or minimising settlements.

A pre-condition survey of all potentially affected structures should be undertaken prior to

commencement of tunnelling works

Structural methods such as



• Underpinning

• Jacking

• Jet Grouting

• Compensation Grouting (during and/or after tunnelling)

• Curtain walling (Sheet piles, diaphragm walls, contiguous bored piles, mini piles)

• Strengthening of affected structures

Ground improvement methods such as

• Consolidation grouting

• Vibro compaction/replacement of soils before tunnelling

• Ground Freezing

Tunnelling methods such as

• Use of support fluids during tunnelling

• Use of tunnel shield

• Re-alignment of tunnel (horizontal or vertical) to avoid/minimise impacts on sensitive

structures

Planning methods such as

• Property purchase

• Demolition

• Relocation

Protection of existing services

• In situ re-lining old/brittle service pipes

• Excavation and replacement

• Underpinning

Contract specifications should clearly state the settlement limits to be adopted for the

tunnelling works and should require contractors to provide detailed method statements

describing the method of tunnelling and precautions and procedures to be adopted to control

surface settlements.

4.4.3.6 Remedial actions Unacceptable ground surface movement or any damage to adjacent structures will

necessitate full reinstatement of the affected surfaces or structures in accordance with the

Road Authorities specifications.

Before undertaking any reinstatement a full report shall be submitted documenting the

surface movement and providing an explanation of its cause. This shall include a

geophysical testing of the affected area.

A complete method statement of the planned reinstatement must be submitted and

approved before reinstatement work progresses.



4.4.4 Groundwater Control Due to the risk involved in possible soil displacement, dewatering shall always be kept to an

absolute minimum necessary for satisfactory installation.

Dewatering for NDRC work will generally not be permitted, however localized dewatering for

construction of shafts or for the launch or reception of the tunnelling machine may be

permitted for a limited time.

Dewatering systems, including an appropriate filter around riser pipes, should be carefully

considered and designed properly. The dewatering solutions/design shall be submitted for

approval.

The filter design should ensure against the

possibility of any internal soil erosion that might

cause ground settlement and collapse. Filters

can be either conventional soil filters or geo-

textile filters. The use of geo-textile filters are

preferred and recommended.

Once shafts are constructed these shall be

water tight. It is highly recommended that the

pits be fully sealed using either concrete slabs

or an injection plug. Any pumping of inflowing water from the shaft will be considered

dewatering.

All water removed from any dewatering system must be disposed of in accordance with the

environmental permit.

A detailed description of the required dewatering along with the estimated amounts of water

and their disposal must be submitted for approval along with the Method Statement.

4.4.5 Materials and equipment Pipe materials shall be selected in accordance with the specifications given by the Client. All

materials shall have the capability of withstanding the pulling or pushing forces exerted

during installation along with the long term loads of soil, groundwater and traffic.

Piping and cable materials shall be chosen to withstand corrosion and other chemical

reactions from both the intended media and groundwater.

All joints and connections must be water tight and be designed to withstand the forces

exerted upon them during installation.

The following information must be supplied for all pipe materials:

• Manufacturer

• Grade/strength

• Outside diameter

• Thickness

• Material composition including any coating



• Connection or joint details

For any drilling fluids or grouts:

• Ingredients, including material safety data sheets

• Design mixes, viscosity, density, etc.

Equipment and machinery:

• Manufacturer

• Manufactured date

• Model or type

• Thrust and/or pulling capacities

• Calibration certificates

4.4.6 Method of statements The Method Statement shall include all requirements regarding the Contractor's method for

undertaking the works in compliance with relevant designs, specifications, site controls and

restrictions, inspection plans, programme, equipment resources, staff etc.)

A complete Method Statement shall be submitted and approved prior to commencement of

construction, including:

4.4.6.1 Contractor experience Documentation detailing the training and relevant experience of the Contractors personnel

shall be submitted which includes all personnel that would be undertaking the work. All

personnel are required to be fully trained in their respective duties and in the safety of

operating any equipment that will be utilised during the course of the works. The following

shall be submitted:

• Micro tunnelling Qualifications for Contractor Performing Micro tunnelling Work:

• Cover sheet: Date, company name, address, telephone and fax numbers, email

address, and contact person.

• Resumes of managerial, supervisory and operational key personnel:

• Experience in a minimum of 3 previous Micro tunnelling projects of similar size and

scope.

• Detailed descriptions of their Micro tunnelling Projects.

• Summary sheet of previous projects performed using Micro tunnelling that

demonstrates expertise and experience. Named projects may be used more than

once under separate paragraphs if their criteria apply.

• Minimum of 3 years experience performing Micro tunnelling of similar size and scope.

• List 3 separate projects completed using either a Slurry or Earth Pressure Balance

based system.

• Submit for each named project above, and in same order, the following detailed

information:

- Date, full name of project, and location.



- Owner's name, address, telephone and fax numbers, email address, and

contact person

- Client's name, address, telephone and fax numbers, and contact person.

- Employees in charge of work at both head office and site.

- Description of relevant work successfully completed, including ground

conditions.

- Features under which pipe passed, depth below the water table, photos, and

published articles if available.

- Additional information as necessary.

4.4.6.2 Working Drawings Submit specific Working Drawings to include but not limited to:

• Jacking and receiving pit configurations.

• Design and construction of jacking and receiving pits

• Details for ground support system.

• Special requirements for jacking and receiving pit penetrations, thrust blocks,

backstops or other reactions required for Micro tunnelling, casing pipe jacking or any

other jacking.

• Full calculations supporting maximum jacking capacity that jacking pit will withstand

without movement exceeding 0.5 inches with an appropriate factor of safety.

• Areas for storage, material and spoil handling, dewatering, ground stabilization if

required, excavation procedures, and backfilling.

• Dewatering and ground water control plans for all jacking and receiving pits.

4.4.6.3 Construction Works The Contractor shall deliver a detailed time schedule for construction sequencing and

programming, clearly showing the planned activities and the work areas involved.

Supply full details of Micro tunnelling System to be employed.

• Manufacturer and date(s) of manufacture.

• Type and model number for whole system if from single source or separate details

for each element of system.

• Confirmation from manufacturer that machine set up is suitable to limit annular

space, as specified, for external diameter of casing pipe proposed.

• System of alignment monitoring and steering control and activation.

• Hydraulic jacking system maximum capacity and method of limiting jacking capacity

to that of maximum capacity of specified casing.

Supply full details of procedures and resources that will be employed to carry out work

including method and sequence of:

• Establishment of drive line of MTBM and elevation at base of shaft.

• Casing Pipe handling and connections.

• Maintaining line and grade, and re-establishment of line and grade as required.

• Spoil separation and disposal.



• Spoil and slurry containment during Micro tunnelling work.

• Installation of carrier pipe, including placement of grout between carrier pipe and

casing pipe, and procedures to prevent floatation during grouting.

Supply full details of following materials:

• Design mixes for all concrete, grout, or flowable fills. Casing pipe including

manufacturer, grade, and specification, outside diameter, thickness, and any

coatings, if required.

Calculations that clearly state:

• Maximum calculated jacking resistance for installing complete casing.

• Maximum allowable face pressure or slurry pressure that can be exerted at tunnel

face without fluid loss to surface, other structures or features or heave of ground.

• Relationship between hydraulic jacking pressure and force applied to casing pipe

during jacking.

4.4.7 Risk Assessment and Risk Register A risk assessment shall be conducted in accordance with the Risk Management Manual.

The main risks involved in undertaking NDRCs are surface settlement or heave. Other risks

that may be encountered are road user safety that may be derived from surface movement

and risk of damage to existing utilities or structures.

The Contractor must undertake a risk assessment listing all the possible occurrences in a

risk register and evaluated the likelihood and consequences of these occurrences. The risk

assessment shall include analysis and procedures for mitigating risks along with emergency

procedures for dealing with specific incidents.

The various methods of NDRC will have different risks associated with them. A summary of

the level of risk associated with each method is shown in Table 13. This table shall be used

as a guide, and the particular conditions of the specific site shall be taken into consideration.

Table 13: Risk summary for typical NDRC methods

Method Principal risk

Surface settlement Surface heave

Road user safety

Damage to existing utilities

Impact moling Negligible High Moderate Moderate

Pipe ramming (open end) Negligible Moderate Minor Moderate

Auger boring Moderate Negligible Minor Moderate

Horizontal directional drilling Minor Moderate Negligible Minor

Micro tunnelling Minor Minor Negligible Negligible

Pipe jacking Minor Minor Negligible Negligible



Please see Appendix A for a list of potential H&S risks for NDRC work. In addition to

highlighting the possible risks, the Contractor must also establish contingency plans for

correction of potential conditions. They include:

• Inability to complete the pilot hole

• Excessive fluid loss/hydraulic fracturing

• Inability to pull the pipe

4.4.8 Procedure and logistics for obtaining No Objection

Certificates No Objection Certificates (NOCs) must be obtained from all concerned utilities agencies or

stakeholders that may be affected by the NDRC. A list of the Authorities as a guide but not

limited to those are contained within Appendix A .

Note: Some of the utilities or other authorities may require 2-4 weeks to give NOCs or even

longer, if insufficient information is supplied. The Contractor must make sure that the Town

Planning approval is valid.

4.4.8.1 Conflict with other Utilities The Contractor/Sub Contractor is required to obtain information on all existing utility lines in

the vicinity of the work area prior to commencing of any excavation. If there is uncertainty as

to the exact location of any utility it may be necessary for trial pits to be excavated. Such

details are to be included in the approved Method Statement

Suggested minimum safe distances between the different utilities are shown in Appendix C.

The relevant Authorities should be contacted for approval to dig near their utilities. The most

up-to-date codes and standards are to be adopted.

It is always the Contractor/Sub Contractors' responsibility to ensure that he has obtained all

information on other utilities in the work area and that he has assessed the safe distances to

these. Any damage to any utility during the undertaking of the NDRC is the sole

responsibility of the Contractor/Sub Contractor.

The minimum distances away from existing utilities must be followed. These are detailed in

Appendix C. However the Contractor must approach the relevant Authorities for details on

the latest standards for the particular crossing implemented.

4.5 During Construction The Contractor/Sub Contractor shall keep updated records at the work site for the duration

of the work. A checklist of minimum daily routines for monitoring and record keeping is given

in Appendix D. The records shall be checked and signed by the supervising Consultant.

A Project Board must be generated and installed detailing the specific project details and

contact details of the relevant stakeholders.

4.5.1 Monitoring of Surface Movement For purposes of monitoring ground surface movement on the roadway, the Contractor shall

install flush-head pins (35.0 millimetres to 50.0 millimetres in length) in the road pavement.



These pins shall be the monitoring points. The pins shall be installed in a grid pattern at

approximately 2.0m centres.

The location of monitoring points and reference benchmarks are to be submitted before

construction. Approval shall be sought from a Road Maintenance Consultant nominated by

the DoT.

The grid of monitoring points shall cover the entire width of the roadway along the drive and

shall extend outwards in each direction from the centreline of the drive to a distance of the

drive centreline depth below the road surface.

Measurements shall be replicable to a level of 0.5 mm and shall be done on a daily basis

during construction.

Ground surface movement outside the acceptable limit shall be immediately reported to the

Road Authority and remedial actions taken.

Ground surface movement limits in the specified area shall remain in effect for 2 years from

date of completion of the NDRC and shall be monitored on a monthly basis.

The records to be kept by the Contractor and supplied to the Overseeing Organisation

should be established prior to any construction works.

The type of records will vary for each method and project but the following information

should be recorded where applicable, is listed in Table 14.



Table 14: Type of records for NDRC projects

4.5.2 Instrumentation Requirements The following data shall be recorded, if possible automatically, during installation:

For micro tunnelling:

• Line and level

• Maximum jacking forces of the main, and if used, intermediate thrust stations

• Jacking speed/distance

Micro

Tunnelling &

Pipe Eating

Pipe

Jacking

Directional Drilling Auger Boring Pipe Ramming Impact Moling

Contract * * * * * *

Reference of pipe run

* * * * * *

Date of work * * * * * *

Start time * * * * * *

Finish time * * * * * *

Details of any

stoppages

* * * * * *

Diameter of

bore

* * * * * *

Pipe material * * * * * *

Pipe diameter * * * * * *

Joint packing * * * *

Length installed * * * * * *

Main survey

checks

* * * * * *

Soil conditions * * *

Ground water

level

* * *

Line and level

achieved

* * * * * *

Lubrication * * *

Support Fluid *

Jacking &

winch loads,

w.r.t. progress

* * *

Slurry pressures,

viscosity, discharge, flow

rate

* * *

Shield role,

pitching, steering

adjustment

* * *

Thrust rate,

cutting torque,

soil discharge

* * *

Interval at

which

measurements

should be taken

Grout materials

and volumes



• Quantity of slurry and if possible of excavated soil

• Rolling

• Steering correction

• Maximum interval of recordings should be every 0.2 m of excavation.

The following should be confirmed before and during construction:

• Closed face capable of providing adequate supporting pressure to excavated area

• Use slurry pressure and/or auger earth pressure to achieve the balance of earth and

ground water

• Make sure of the ability to control axial rotation and steer to correct vertical and

horizontal deviation from alignment by remote activation

• Means to inject lubricant over lead pipe, if required

• The spoil transportation system has capacity for removal and balancing of spoil.

• The slurry system operates so that excess fluid can be discharged safely

• Control system enables remote control of all main functions of the system from one

location

For manned techniques:

• Line and level

• Maximum jacking forces of the main and if used intermediate thrust stations

• Jacking speed/distance

• Quantity of slurry and if possible of excavated soil

• Rolling

Maximum interval of recordings should be once per pipe section installed.

For horizontal directional drilling:

• Line, level and length

• Quantity and characteristics of drilling fluid

• Maximum pulling forces

Maximum interval of recordings should be once per drilling rod.

4.5.3 Equipment Performance Requirements Closed face capable of providing positive supporting pressure to full excavated area (face) at

all times and capability of controlling and measuring pressure at face.

Achieve balancing of earth and ground water pressures by use of slurry pressure, auger

earth pressure balance or a combination of the two.

System capable of any adjustment required to maintain face stability for anticipated ground

conditions.

Control slurry pressure systems, using slurry spoil transportation, earth and groundwater

pressure at the face by use of variable flow slurry pumps, pressure control valves and

minimum of 2 flow meters, one on feed side and side, and one on return side.



For earth pressure balance systems using a screw auger spoil transportation from the face,

control excavated material by maintaining an earth pressure balancing plug of material at the

plug of material at the face with advance of system being matched with excavation removal

through auger. Control soil through auger by use of pitch spacing and/or an auger gate or

throttle.

Sufficient power and ability in normal operation to cut or crush hard material of sizes up to

1/3 internal diameter of pipe and up to 30,000 psi compressive strength.

Ability to control axial rotation to within 3-degrees of normal operating datum.

Ability to articulate and steer to correct vertical and horizontal deviation from alignment

datum by remote activation.

Means to inject lubricant over lead pipe, if required.

Spoil transportation system that has capacity for removal of spoil in balance with excavation

and advance.

Slurry system:

• Spoil separation system sufficient capacity to remove solids from flow while system is

excavating spoil.

• Operates in such a manner that re-circulated or excess fluid can be discharged

safely and with negligible remaining fines.

Overall control system that enables remote control of all main operating functions of system

from one location, either at surface or within jacking shaft.

Main jacking pit capable of exerting uniform load to casing pipe at a speed commensurate

with speed of excavation advance.

Set jacking hydraulics to relieve pressure at maximum safe working capacity of casing pipe.

4.6 After Construction After construction, all details of the completed NDRC work shall be collected and submitted

to the Road Authority including test certificates and relevant Contractor’s notes/reports. A

checklist of required information and documentation is given in Appendix D.

4.6.1 Inspection and testing Pipe inspection and testing shall be carried out according to the Client’s specifications.

An infiltration test of the permanent construction should be carried out to verify that the

pipeline, joints/connections are water tight. The infiltration test shall first be carried out after

any dewatering is stopped and the groundwater has attained normal levels.

If requested by the DoT, CCTV inspections should be carried out to ensure that the inside of

the pipeline is structurally sound. Man entry pipes shall be visually inspected only. The

inspection should include:



• Line and level

• Joints

• Damage

• Deformation

• Connections

• Linings and coatings

Any leaks shall be recorded, and repaired as appropriate. All records should be submitted to

the DoT. The grouting will also need to be checked and certified as applicable to the ground

conditions.

4.6.2 Site clearance and decommissioning After completion, the working areas shall be cleared and reinstated to their previous

condition. All equipment, materials shall be removed and excess spoils and waste shall be

disposed of in an approved and environmentally suitable way.

Working shafts shall be backfilled with suitable compacted materials in accordance with the

Specifications. Shoring or other temporary shaft materials shall be removed or cut to a level

minimum 1.5 m under surface level.

A checklist should be developed by the Contractor and submitted to the DoT. Some

suggested points are contained within a checklist in Appendix A

4.6.3 Monitoring/inspection for long term (latent) defects The Contractor shall carry out monitoring of ground surface movement, as described in

Section 3.4.1, two years after completion and report monthly any changes to the Road

Authority.

A visual inspection of the working area and surrounding structures shall be done at the same

time and any defects that may have been a consequence of the NDRC work shall be

included in the report.

4.6.4 QA/ QC Methodology Quality Assurance and Quality Control are key factors in a successful NDRC undertaking.

The Contractor shall implement a Quality Assurance Plan (QAP) outlining proposed points

where quality controls will be performed.

These shall include but not necessarily be limited to:

• Check and approval of all working drawings and method statement.

• Location of any other utilities or structures have been correctly identified and marked.

• Pipe/cable materials conform to specifications and quality documentation from

manufacturer has been acquired.

• Line and level of proposed NDRC have been checked including guidance system.

• Check of machinery and other equipment.

• During installation; check of rate of advancement, drilling pressure, torque, pulling

forces, etc.



• Check of flow and pressure of any drilling fluids or lubrication.

• Amount of soil excavated is registered and checked in conjunction with theoretical

values.

• Any dewatering installations are checked and flow registered.

• Any deviations or unexpected developments are registered and investigated.

• Surface movements are monitored in accordance with this manual.

• After completion the line and level are surveyed and registered and documented.

A minimum requirements checklist to be followed before commencement of works is

included in Appendix A

All controls and information are to be gathered/documented and kept at the work site for any

inspections.

Please refer to the DoT’s QAQC Requirements document for further information.

.

January 2013

APPENDIX A: CHECKLISTS FOR SUBMITTALS

A.1. Checklist of submittals for approval of preliminary

design

The following information or documents shall as a minimum be submitted for preliminary

approval (pre-tender) of NDRC design.

Nr Requirement

1 NDRC Application form

2 Approval letter from Abu Dhabi Town Planning

Drawings:

3 Map of site location

4 Plan of line, level and diameter

5 Profile section of proposed drive

6 Plan of work site area showing working shaft locations and sizes

7 Plans showing other utilities

Geotechnical:

8 Preliminary sources study

9 Ground investigation factual and interpretative reports

10 Profile section showing soil conditions along the proposed drive

January 2013

A.2. Checklist of submittals for approval of construction

The following information or documents shall as a minimum be submitted for final approval

of design and approval of construction:

Nr Requirement

1 NDRC Application form

2 Approval letter from Abu Dhabi Town Planning

3 Approval request letter from design consultant for design and supervision addressed to highway section (Arabic)

4 Approval request from Contractor with confirmation of the Sub Contractor name

5 Undertaking letters from the Client, main Contractor and NDRC Sub Contractor as per DoT forms

6

Method statement including detailed description of method, sequencing and program of work, key qualifications and references, list of equipment and materials, ground water control, safety procedures and risk assessment

Drawings:

7 Map of site location

8 Plan of line, level and diameter

9 Profile section of proposed drive

10 Plan of work site area showing working shaft locations and sizes

11 Plans showing other utilities

12 Details of shafts including entry and exit seals

Calculations:

13 Design calculations of pipe materials with max. permissible forces

14 Design calculations of shafts

15 Surface movement calculations

Geotechnical:

16 Preliminary sources study

17 Ground investigation factual and interpretative reports

18 Profile section showing soil conditions along the proposed drive

19 No Objection Certificates (NOC) from utility agencies, property owners, police and other relevant authorities

20 Bank guarantee (6000 AED per m length )

January 2013

A.3. Checklist of Potential H&S Hazards & Risks

The following are considered potential Health and Safety risks for NDRC work to be

considered by the Contractor. This list is not exhaustive and is to be expended depending

on site conditions/location

Nr Potential Risk

1 Road User/Public Awareness of Works

2 Site Workers Training/Ability

3 Confined Spaces

4 Damage to Existing Utilities

5 Damage to Equipment

6 Unexpected Ground Conditions

7 Failure of Traffic Management System

8 Surface Heave

9 Surface Settlement

10 Excavation collapse

11 Poor maintained equipment

12 Adjacent structures

13 Adjacent works

A.4. Checklist of Authorities for NOCs

The following is a list of Authorities who will need approaching for approval to dig. This list is

not exhaustive.

Nr Items

1 Abu Dhabi Municipality, Town Planning & Survey Directorate

2 Abu Dhabi Municipality, Roads Section

3 Abu Dhabi Municipality Public Gardens Directorate

4 Al Ain Municipality

5 Western Region Municipality

6 TRANSCO (Water and Electric)

7 Abu Dhabi Distribution Company, ADDC (Water & Electricity Authority)

8 Abu Dhabi Sewage Services Company, ADSSC (Sewer)

9 Etisalat (Telephone Authority)

10 DU (Telephone)

11 GASCO (Gas Authority)

12 Dolphin Energy (Gas Authority)

13 ADNOC (Oil)

14 TAKREER (Oil)

15 GHQ Armed Forces (Fibre optic cables)

16 Critical National Infrastructure Authority, CNIA

January 2013

A.5. Checklist of QAQC Issues

The following is a list of potential QAQC issues to be checked and signed off before

construction commences.

Nr Items

1 The supervisor has previous experience with the specific construction method being used

2 The personnel performing the operations have the relevant expertise/prior knowledge

3 The manufacturer’s instructions are being followed

4 Set up procedures are complete

5 The materials are ready and to hand before commencement

6 The supervisor has previous experience with the specific construction method being used

7 The personnel performing the operations have the relevant expertise/prior knowledge

8 The manufacturer’s instructions are being followed

A.6. Checklist of Post-Construction Checks

The following is a list of potential issues to be checked and signed off following construction.

This list is not exhaustive and is to be expended depending on site conditions/location.

Nr Items

1 Have all excavations been backfilled?

2 Have all materials been removed from the site area?

3 Has all machinery been removed from the site area?

4 Has all traffic management signage and protection been removed?

5 Is the surface in a clean state and as per the commencement of the works?

6 Has all vegetation been replaced/reinstated?

7 Have all excavations been backfilled?

January 2013

APPENDIX B: FORMS AND EXAMPLES OF LETTERS FOR

APPLYING FOR NDRC WORKS

B.1. Required forms and examples of letters

The following forms and letters must accompany all applications for undertaking NDRC

work.

1. DoT Road Crossing Application Form

2. Approval request letter from design consultant for design and supervision addressed

to the highway section (Arabic)

3. Approval request from Contractor with confirmation of the SubContractor name

4. Undertaking letters from the client, main Contractor and NDRC SubContractor as per

DOT forms (Arabic)

5. Bank Guarantee (Example)

January 2013

January 2013

Conditions for NOC for Micro-tunnelling Works

Project:

Owner Authority:

Consultant:

Contractor:

Micro-tunnelling Works Contractor:

Excavation Details:

No. of

crossings

Crossing

Location

Maximum

Tunnel

Diameter

Minimum

Depth (From

Asphalt

Surface to the

Top of the

Pipe)

Tunnel Length

Under the

Road

Conditions:

1- Obtain approval of all concerned service authorities prior to proceed with any works in the site.

2- It is “strictly” forbidden to carry out or delegate any works subject of approval to any other Contractor other than the above approved Contractor for carrying out microtunneling excavation, even if he is the main Contractor, without DoT approval, where bank guarantee will be seized in case you fail to commitment to the above mentioned.

3- The (NOC) is limited only for the above indicated excavation areas, and in accordance to the details shown next to them.

January 2013

4- If the site geotechnical report shows a layer of weak soil at the excavation level, the Contractor should do stabilization to the soil prior to commence excavation works.

5- The microtunneling Contractor and Sub-Contractor, should commit to the submitted working method without prejudice its steps.

6- The submitted bank guarantee does not represent the cost of repair of land subsidence in case of occurrence, it is a guarantee until the end of the period of supervising the excavation area by microturnelling and the real cost will be determined at the time, no matter how much.

7- The control period of microturnelling excavation area is (two years) starting from date of the Consultant confirmation on completion of maintenance works on site according to the specifications and the submitted and approved working method.

8- Works should not be commenced unless an official site handing over record is made (including the sites, the control points’ levels at the time, and colored photos for the excavation location) in presence of the project Consultant/ [[., DoT road maintenance Consultant in the area/ [[[[, the main Contractor and the excavation Contractor.

9- The undersigned project Consultant staff should make sure of the Contractor and the Sub-Contractor commitment to the submitted work method, and retain photos for the work phases and record of full data and reads of the excavation machine starting from commencement date to completion date, a copy of which is to be submitted to DoT after completion of work.

10- Under the supervision of the Consultant, the Contractor and microtunneling excavation Sub-Contractor shall make arrangements required to maintain asphalt surface subsidence level within the limit allowed (6mm). In case that allowed limit is being exceeded; the Consultant should inform Road Department directly and without any delay.

11- The depth between asphalt surface and the top of the tunnel should not be less than what is stated in the submitted work method (shown above).

12- The tunnel diameter should not exceed what is stated in the submitted work method.

January 2013

13- The distance between the edge of the push pit and the receiving pit and the road (sub-grade) edge should not be less than 5m minimum.

14- The asphalt surface subsidence control points should be fixed at a shape of net with dimensions of 2m. This net should cover the road full width along the tunnel at both sides at a distance not less than the distance between the tunnel center and the asphalt surface. Also readings should be taken (under the Consultant/Owner Authority supervision) prior to commence and during carrying out these works (at rate of 3 times for each work shift), and after execution (as shown in the submitted working method), provided that the benchmark should not be less than 50m from the tunnel location.

15- The supervision staff (Consultant/Owner Authority) should submit all the records related to the road surface control points readings, officially and regularly every month to the Technical Support Section in the Main Roads Department.

16- All security and safety precautions should be taken at the push pit and the receiving pit, and also the suitable warning signs to ensure the safety of the pedestrians and vehicles day and night according to the necessary conditions of Abu Dhabi Police and DoT.

17- The two pits’ should be re-filled after work completion on layers and to remove all the debris and reinstate the site.

18- If it is necessary to process a dewatering, it should be carried out by the

approved way and without affecting the soil characteristics.

19- To coordinate with the Maintenance Consultant in Roads and Technical Services Department who is supervising the maintenance of the area in which the excavation will take place.

20- To submit to DoT two copies of the “As Built Drawings” for the works already implemented approved by the project Consultant after work completion, along with an official letter from the project Consultant.

We recognize that we have learned all the conditions (1-20) and confirm our

agreement and our commitment to them, and we accordingly sign:

Consultant:

January 2013

Name:

Position:

Contractor:

Name:

Position:

Microtunneling Sub-Contractor:

Name:

Position:

January 2013

Declaration and Undertaking

We, Company/Department of [[[[[[[[., acknowledge that in the event

of any subsidence or damages to roads or road facilities, other than what is

permitted according to DoT regulations, at [..[[ area in which the main

contractor/ company [[[[[..and micro-tunnelling works Contractor,

M/s[[..[.[.type approved by the us M/s[..[[[[.is undertaking

excavation works, we will immediately inform DOT and undertake to make

necessary repairs according to DOT specifications or deduct the cost of repairs

from the main contractor in favour of DOT immediately when the subsidence

takes place, at request of DOT without delay or review and shall pay

compensation for any accident caused by this subsidence.

I hereby agree and accept the above.

For the Company[..

Name:[[[[[

Designation:[[[[

Signature & Seal:-[[[..

Date:-[[[[[..

To be signed by Authorised person, letter of authorization shall be enclosed.

January 2013

Template for Bank Guarantee

Department of Transport

P.O.Box 20

Abu Dhabi

United Arab Emirates

Dear Sir

RE: PERFORMANCE GUARANTEE NO. ________ FOR AED________ FOR NON-

DISRUPTIVE ROAD CROSSING OF ___________________ ROAD

We, (insert name and address of bank) hereby guarantee to pay to the Depertment of

Transport, P.O.Box 20, Abu Dhabi, UAE, the sum of AED___________ (UAE Dirhams

____________________________) on account of (insert company name and address) as a

guarantee for the due and propert performance of the subject work.

1. This Guarantee shall be paid to the Department of Transport on first demand without

any proof of condition.

2. This Guarantee shall be valid for 1 (one) year from ________ until ________ and

shall before expiry, be automatically renewed until the Final Acceptance Certificate

has been issued by the Department of Tranport.

This Guarantee is issued under the official seal of the bank and signed by the required

authorized signatories.

Yours faithfully

________________

January 2013

APPENDIX C: SUGGESTED MINIMUM SAFE DISTANCES

BETWEEN UTILITIES

January 2013

APPENDIX D: CHECKLISTS FOR MONITORING DURING AND

AFTER CONSTRUCTION

D.1. Daily requirements

The following checklist contains the minimum requirements of monitoring and data collection

on a daily basis during construction. This shall comprise of, but not necessarily be limited to:

Nr Requirement

1. Numbers of personnel and equipment on site (names, positions, etc)

2. Inspection of work site fencing, traffic barriers, signs, safety checks, etc

3. Installed length of pipe (types, times etc)

4. Line and level measurements

5. Any vertical or horizontal deviations from planned line

6. Instrumentation readings of jacking, drilling or pulling forces

7. Slurry or bentonite usage and pressure readings

8. Amount of excavated soil or spoils removed

9. Monitoring reports of surface movement

10. Check and inspection of delivered materials

11. Check of machinery and other equipment

12. Any accidents or unexpected events - their cause and actions taken

All reports shall be approved and signed by the supervising Consultant.

January 2013

D.2. After construction

The following checklist contains the minimum requirements of monitoring and data collection

on a daily basis during construction. This should be collated and submitted by the Contractor

or Sub-Contractor and shall comprise of, but not necessarily be limited to:

Nr Requirement

1. Line and level measurements updated on As Built drawings

2. Infiltration test documenting the pipeline is water tight, including details on the testing analysis and techniques

3. CCTV or other report of internal inspection, highlighting any deformation or irregularities (in DVD format)

4. Documentation of installed pipe materials (manufacturer, type, etc.)

5. Any vertical or horizontal deviations from planned line (to be shown in profile sections)

6. Instrumentation readings of jacking, drilling or pulling forces (report format)

7. Slurry or bentonite use and pressure readings (report format)

8. Quantities of excavated soil or spoils removed

9. Monitoring reports of surface movement, including details on the methods used for calculation

10. Reports of accidents or unexpected events - their cause and actions taken

11. Post-construction site survey, including electronic copy

12. Construction photographs and/or video as appropriate

13. Documentation of correct backfilling and compaction of shafts including compaction test results

14. Report showing that work site has been cleared and all waste removed

All reports shall be approved and signed by the supervising Consultant.

January 2013

Appendix E

Internal dimensions for pipejacks and tunnels below 3.m diameter and indicative drive lengths

January 2013

January 2013

CITED REFERENCES

January 2013

OTHER REFERENCES

January 2013

GLOSSARY

Specialized terms, abbreviations and acronyms frequently used in this manual are listed and

defined below. Where a term, abbreviation or acronym is defined in another Department of

Transport Manual, that definition is applied to this manual by reference.

Auger Boring: Method for forming a bore, usually from a drive pit, by means of a rotating

cutting head. Spoil is removed back to the drive pit by helically wound auger flights rotating

in a steel casing. The equipment may have limited steering capability. See also Guided

Auger Boring.

Back Reamer: Cutting head attached to the leading end of a drill string to enlarge the pilot

bore during a pull-back operation to enable the product pipe to be installed.

Bore: Void which is created to receive a pipe, conduit or cable.

Cased Bore: Bore in which a pipe, usually a steel sleeve, is inserted simultaneously with the

boring operation. Usually associated with auger boring or pipe jacking.

Casing: Pipe to support a bore. Usually not a product pipe.

Cutting/Cutter Head: Tool or system of tools on a common support that excavates at the

face of a bore. Usually applies to mechanical methods of excavation.

Directional Drilling: Steerable method for the installation of pipes, conduits and cables in a

shallow arc using a surface launched drilling rig. In particular, the term applies to large scale

crossings in which a fluid filled pilot bore is drilled without rotating the drill string, and this is

then enlarged by a washover pipe and back reamer to the size required for the product pipe.

The required deviation during pilot boring is provided by the positioning of a bent sub.

Drill Bit/Head: Tool which cuts the ground at the head of a drill string, usually by mechanical

means.

Drilling Fluid/Mud: Mixture of water and usually bentonite or polymer continuously pumped

to the cutting head or drill bit to facilitate the removal of cuttings, stabilise the bore, cool the

head and lubricate the passage of the product pipe. In suitable ground conditions water

alone may be used.

Drill String/Stem: The total length of drill rods/pipe, bit, swivel joint, etc. in a bore.

Drive/Entry Shaft/Pit: Excavation from which trenchless technology equipment is launched

for the installation or renovation of a pipeline, conduit or cable. It may incorporate a thrust

wall to spread reaction loads to the ground.

Earth Pressure Balance (EPB) Machine: Type of microtunnelling machine in which

mechanical pressure is applied to the material at the face and controlled to provide the

correct counter-balance to earth pressure in order to prevent heave or subsidence. The term

is usually employed where the pressure originates from the main jacking station in the drive

January 2013

shaft or to systems in which the primary counter-balance to the earth pressures is supplied

by pressurised drilling fluid or slurry.

Face Stability: Stability of the excavated face of a tunnel or pipe jack.

Grouting: Method of filling voids, usually with cementitious grout.

Guided Auger Bore: Method of auger boring in which the guidance mechanism actuator is

sited in the drive shaft. The term may also be applied to those auger boring systems with

rudimentary articulation of the casing near the cutting head activated by rods from the drive

shaft.

Guided Boring: See Guided Drilling.

Guided Drilling: Method for the installation of pipes, conduits: and cables using a surface-

launched drilling rig. A pilot bore is drilled using a rotating drill string and is then enlarged by

a back reamer to the size required for the product pipe. The necessary deviation during the

pilot boring is provided by a slanted face to the drill head, an asymmetric drill head, eccentric

fluid jets or a combination of these, usually in conjunction with a locator.

Guide Rail: Device used to support or guide, first the shield and then the pipe within the

drive shaft during a pipe jacking operation.

Heaving: Process in which the ground may be displaced causing a lifting of the ground

surface.

Horizontal Directional Drilling (HDD): See Directional Drilling.

Impact Moling: Method of creating a bore using a pneumatic or hydraulic hammer within a

casing, generally of torpedo shape. The term is usually associated with non-steered or

limited steering devices without rigid attachment to the launch pit, relying upon the

resistance of the ground for forward movement. During the operation the soil is displaced,

not removed. An unsupported bore may be formed in suitable ground, or a pipe drawn in, or

pushed in, behind the impact moling tool. Cables may also be drawn in.

Impact Ramming: See Pipe Ramming.

Jacking Force: Force applied to pipes in a pipe jacking operation.

Jacking Pipes: Pipes designed for use in a pipe jacking operation.

Jacking Shield: Fabricated steel cylinder from within which excavation is carried out, either

manually or by mechanical means. Incorporated within the shield are facilities for controlling

line and level.

Launch Pit: As for drive pit but more usually associated with launching an impact moling or

similar tool.

Locator: An electronic instrument used to determine the position and strength of

electromagnetic signals emitted from a transmitter sonde in the pilot head of a boring

system, in an impact moling tool or from existing underground services that have been

energised. Sometimes referred to as a Walkover System.

January 2013

Microtunnelling: Method of steerable remote control pipe jacking to install pipes of internal

diameter less than that permissible for man-entry. In North America the term is used to

describe remote control continuous pipe jacking in all diameters.

Pilot Bore: First, usually steerable, pass of any boring operation that later requires

backreaming or other enlargement. Most commonly applied to guided drilling, directional

drilling and 2-pass microtunnelling systems.

Pipe Jacking: Method for directly installing pipes behind a shield machine by hydraulic or

other jacking from a drive shaft such that the pipes form a continuous string in the ground.

Pipe Ramming: Non-steerable method of forming a bore by driving a steel casing, usually

openended, with a percussive hammer from a drive pit. The soil may be removed by

augering, jetting or compressed air. In appropriate ground conditions a closed casing may be

used.

Product Pipe: Permanent pipeline for operational use.

Pull-Back: That part of a guided drilling or directional drilling operation in which the drill

string is pulled back through the bore to the entry pit or surface rig, usually installing the

product pipe at the same time.

Reception/Exit Shaft/Pit: Excavation into which trenchless technology equipment is driven

and may be recovered during the installation or renovation of a product pipe, conduit or

cable.

Rod Pushing: Method of forming a pilot bore by driving a closed pipe head with rigid

attachment from a launch pit into the soil that is displaced. Limited steering and monitoring

capability may be provided, usually in conjunction with a locator.

Subsidence: Process in which the ground may be displaced causing a settlement at the

surface.

Target Shaft/Pit: See Reception/Exit Shaft/Pit.

Thrust Pit: See Drive Pit.

Trenchless Technology: Methods for utility and other line installation, rehabilitation,

replacement, renovation, repair, inspection, location and leak detection, with minimum

excavation from the ground surface.

Uncased Bore: Self-supporting bore without a lining or inserted pipe, whether temporary or

permanent.

Walkover System: See Locator.

(Reference: International Society of Trenchless Technology, ISTT)

non disruptive road crossings (1)

Documents