Introduction to Trenchless Methods

Introduction to Trenchless Methods

Presented by

Glenn M. Boyce, PhD, PESenior Associates

Presented by

Glenn M. Boyce, PhD, PESenior Associates

April 21, 2009

Presentation Objectives

• Provide a better understanding of trenchless methods used for new installations

• Learn the advantages and limitations of the methods

• Discuss contractor qualifications

Types of Infrastructure

• Gas – Pressure

• Water – Pressure

• Sewer – Gravity

• Drainage – Gravity

• Power – Non-gravity

• Communications – Non-gravity

Trenchless Methods• Impact moling• Pipe ramming• Auger boring• Pilot tube• Pipe jacking / Microtunneling• Conventional tunneling• Horizontal directional drilling• Pipe bursting

Generic Size and Length

• Method Size LengthMoling 2” - 12” 150’Ramming 8” - 72” 300’Auger Bore 8” - 60” 250’Pilot Tube 6” - 42” 300’Microtunneling 12” - 108” 1,500’Pipe Jacking >54” 3,000’HDD 2” - 48” 6,500’Tunneling >60” Any length

What to Do?

• Choose the right method

• Use established “Standards”

• Collect information/investigate

• Plan ahead

• Conduct risk assessments

• Include mechanisms to handle conflicts

Use the Right Method• Open cut• Horizontal Directional Drilling• Auger boring• Pipe ramming• Pipe jacking• Microtunneling• Tunneling

1996

Pilot Tube

Auger Boring

• Road crossings

• Cohesive soils

• Short distances

• Above water table

• Need steel casing

• Minor steering

60-inch Diameter SBU-A

Pilot Tube Method

• Medium distances

• Straight alignments with good accuracy

• Variety of soils

• Smaller shafts

• Moderate equipment costs

Step 1

•

•

•

Step 2•

Pilot Tube + “Plus”

• Now used as a guide for other method– Auger boring

– Pipe Ramming

Pipe Ramming• Wide range of

diameters• Soils only• Continuously

supported• Typically < 300’• Above and below

water table• Need steel casing• No steering control

Installation Method• Ramming in continuous length or segments

Rammingin

Progress

Pilot tube

Pipe Jacking

• Large diameters • Soils and mixed

ground• Face supported• Long distances• Above the water

table• Steerable

Microtunneling

• Range of diameters (> 12”)

• All ground types

• Continuous face support

• Long distances

• Above or below water table

• Range of pipe materials

• Steerable to line and grade

Micro vs Utility TunnelingRemotely operatedPrecise guidancePipes jacked from launch pitContinuous support to face

Conventional Rib & Lagging Tunnel

Microtunnel

Tunnel Shield Construction

Lining is built within shield. Lining does not move longitudinally after placement.

Required Axial Thrust versus Length of Drive for Same Diameter

Opposite Approaches

• Open Cut

• What happens happens

• Trenchless

• Understand and plan

What to Do?

• Understand the site history and potential obstructions

• Look at old aerial photos• Conduct a

geotechnical program

• Locate all utilities

Potential Obstructions

• Cobbles or Boulders

• Wood

• Fill materials

• Hard zones

• Mixed faces

Typical Machine Sizes

• Piercing – 2 to 3 inches

• Pilot Tube – 6 to 36 inches

• HDD – 6 to 54 inches

• Auger Boring – 10 to 60 inches

• Pipe Jacking/MT – 12 to 96 inches

• Pipe Ramming – 12 to 144 inches

• Shield – 60 to 144 inches

Typical CMP Culverts

Replacement Issues

• Need to increase size for aquatic passage

• Must keep existing culvert active during construction

• Minimize costs

• Develop the best cross section

• Use the right materials

Possible Solutions

Consume the Culvert

Use Liner Plate Tunnel

Design Solutions

• Built a parallel pipe barrel – Increases capacity

– Allow the existing to remain in service

– Get to use the materials you want

• Slipline the existing after new

• Built a new entry and exit apron

Closing Thoughts

• Methods still evolving

• Many hybrid methods emerging

• Better alignment control emerging in auger boring applications

• Must identify potential obstructions (or get X-ray vision)

HORIZONTAL DIRECTIONAL DRILLING (HDD)

Samuel T. Ariaratnam, PhD, PEArizona State University

Background Lengths up to 8,400 feetLengths up to 8,400 feet

Diameters of 2” – 54”Diameters of 2” – 54”

Applications:Applications: Utility conduitsUtility conduits PipelinesPipelines Gravity sewersGravity sewers Force mainsForce mains Horizontal remediation wellsHorizontal remediation wells Geotechnical investigationsGeotechnical investigations

Pilot Bore and Tracking

Pilot Bore

Drill Bits

Reaming/Hole Enlargement

Reaming

Reamers

CLAY

ANNULAR SPACE REGION

SAND

ANNULAR SPACE REGION

Pipe Material Distribution

Underground Construction Magazine9th Annual Survey, June 2007

Conclusions• HDD is a minimally-intrusive trenchless

construction method suited for highly congested urban areas and high traffic zones

• Horizontal Directional Drilling equipment is capable of installing a wide range of utilities

• HDD will never replace traditional open-cut methods; however, they complement each other

PIPE BURSTING

Samuel T. Ariaratnam, Ph.D., P.E.Arizona State University

Pipe Bursting

• Lengths typically 300-600 ftLengths typically 300-600 ft

• Diameters up to 42”Diameters up to 42”

• Applications:Applications:– replacement of force mainsreplacement of force mains– replacement of gravity replacement of gravity

sewerssewers

Static HeadStatic Head

Pneumatic HeadPneumatic Head

Pneumatic Systems - Usually include a pneumatic tool and winch and bursts the pipe using the kinetic energy of the tool. The pipe is usually attached to either the burst head or tool.

Static Systems – Usually include a hydraulic power source and a rod shuttling system and use high tonnage to pull new line into place.

Small Portable Systems - Either pneumatic or static for doing small diameter and short runs (e.g. laterals).

Common Types of Bursting Systems

IntroductionIntroduction

Emerging field of pipe replacement “Replacement of the host pipe by

fragmenting the existing conduit and installing a completely new pipe of equal diameter or larger in its place.”

ApplicationsApplications

Total pipe replacement Typical upsize as much as 20 – 30% Industrial & Municipal - Main Line &

Laterals Various host and product pipe materials Continuous or Sectional pipe installation

Pipe Bursting Feasibility

May achieve lower costs compared to open trench Less construction time Minimal excavation Social cost savings Reduces ground settlement Low environmental impact

Static Method (Continuous)

Static Method (Sectional)

Pneumatic Method

Almost all types of pipe can be burst …

• Cast iron• Steel• Ductile iron• High Density

Polyethylene• Polyvinylchloride

• Concrete• Reinforced

concrete• Asbestos cement• Clay

Various Host

MaterialsSTEEL

CAST IRON

VITRIFIED CLAY

350mm350mm(14”)(14”)

750mm750mm

(30”)(30”)

650mm650mm(26”)(26”)

Conclusions• Pipe bursting is the only trenchless

method capable of installing a new pipe of equal or larger diameter as a replacement option

• Almost any type of existing pipe can be burst and replaced with most pipe materials

• Proper planning is critical to project success!

CONTRACTOR QUALIFICATIONS & PRE-QUALIFICATION

Introduction

• The majority of trenchless contractors are reliable and follow good installation practices

• However, agencies must be aware of those few “cowboy” contractors

• Qualifying contractors is a recommended practice for trenchless projects to ensure use of competent contractors

Specifications

• Manufacturers Recommended Specifications

• Industry/Association Specification Guidelines

• Project Specific

Testing & Inspection Quality Assurance & Controls in Specifications Trained Inspectors Testing by Owner Laboratory Final CCTV Inspection of the Installed Pipe

Protection of Existing Utilities

• Call in Locates• Obtain As-Built Maps (Shared Responsibility)• Mark Utilities (Utility Owners)• Confirm Utilities (Pothole) (Excavator)• Protect (Excavator)

Protection of Existing Utilities – Locate Marks

As-Builts, Operator Logs, Notes

• Contractor is responsible for marking the plans to indicate any and all vertical and horizontal deviations between the design and actual installation

• Operator logs/notes should be maintained and updated daily by the Contractor and should include–Pipe number, depth, pitch, steering

commands, and notes

Logbook/Field Notes

Contractor Submittals Proof of success on prior similar projects

Pipe material, diameter, length Make/model of equipment, guidance equipment, fluid

mixture Slurry disposal plan Contingency plan Safe plan and protocols Certification by the manufacturer that the Contractor’s

personnel are trained in the use of the equipment Training certification for pipe installation Fusion training certification for HDPE Construction Plan & Installation Schedule Traffic Control Plan

Damage Avoidance

Trenchless Training Courses

• Horizontal Directional Drilling Good Practices

• Pipe Bursting Good Practices• New Installation Methods Good Practices• Cured-in-Place Pipe (CIPP) Good Practices• Sewer Laterals Rehabilitation &

Replacement

(www.nastt.org)

Caltrans Inspector Training

Classroom

Field Exercises

Conclusions• Well-written specifications

are important to minimize claims

• Hiring a competent contractor can be achieved through pre-qualification

• There are numerous available trenchless technology options