concerns on grouting in soils

8/13/2019 Concerns on Grouting in Soils

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GeoEng ConsultantsSPECIALIST CIVIL AND GEOTECHNICAL CONSULTING ENGINEERS


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Concerns on Grouting in Soils

Dr Indrayogan YogarajahDr Indrayogan YogarajahGeoEng Consultants (S) Pte Ltd


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Scope of Presentation

Methods/Forms of grouting

Grouting for Deep Excavation

Effects of Grouting

Overcoming effects

Weed out some misconceptions


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GeoEng Consultants (S) Pte Ltd

Various forms of grouting Jet grouting

Deep Soil Mixing Deep Cement Mixing

Jet Mechanical Mixing

Wet Soil Mixing Chemical grouting

Compaction grouting

Fissure grouting

In fill grouting


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Grouting Grouting of soils is a process of injectinga cementitious compound/mixture into

the ground to minimise one or more ofthe following

Ingress of water (eg. Chemical grouting) Stiffening/strengthening of soils (eg. Jet

grouting, deep soil mixing, deep cement

mixing etc.) Lifting of structures (compaction grouting)

Sealing of gaps in rocks (permeation

grouting, fissure grouting)


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Grouting Soil fracturing

Soil strengthening

Soil compaction

Soil permeation


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Grouting of soilsrouting of soils


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Sealing of CBP, Retaining Wall Service Gap



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Soil improvement for tunnelling



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Underpinning



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Uses of Grouting

Improved soil base forexcavations, especiallyin soft soils (most

common use).- Improve overall

stability

- Reduce ground

movements andsubsidence

- Reduce forces onretaining wall and

strut loads


Improved soil


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Grouting for Deep Excavation

High pressure grouting Jet Grouting (JGP)

Mixing only Deep Soil Mixing (DSM)

Deep Cement Mixing (DCM)

Wet Soil Mixing (WSM)

Grout Mixed Piles (GMP)

Mixing and pressures Enhanced Grout Mixed Piles (EGMP)

Turbo Jet (TJ)

Jet Mechanical Mixing (JMM)

Mixing Methods

High PressureGrouting

Grouting


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Turbo

Enh_d

GMP

WSM

DCM

DSMJGP

GravelSandSiltClayOrganic

RANGE OF SOIL PARAMETERS FOR VARIOUS

GROUTING METHODS


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Concerns of grouting

Design Stage

Strength and Stiffness

Performance of grouting methods Behaviour of Earth Retaining Structures during

Excavation

Construction Stage

Quality of grouting

Heave/settlement and lateral movements of theground and/or Earth Retaining Structures

Performance of Earth Retaining Structures during

Excavation


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Jet Grouting



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Overview Jet grouting used in Singapore for more than 20

years extensive experience. We should not

under-estimate local experience.

Jet grout consist of high pressure water/grout jets

that cuts the soil by disintegrating the soil

matrix. The cut soil is mixed and partially

replaced by the cement grout. As drill string is

rotated and withdrawn, a column of cementmixed soil is formed.



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Overview

Mechanical properties of jet grouted soil is much

like that of sedimentary rocks (e.g. mudstone,

siltstone, sandstone depending of soil jet

grouted).

To understand and apply jet grouting

- Good understanding of soils

- Knowledge of basic fluid mechanics- Knowledge of basic mechanical engineering



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JET GROUTING PROCESS Jet Grout PileJet Grout PileGeoEng Consultants (S) Pte Ltd


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Jet Grout PileGeoEng Consultants (S) Pte Ltd


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3 basic variants

Single tube/fluid

Double tube / fluid

Triple tube / fluid

At present, double tube system is most widely used in

Singapore.

Variants of Jet Grouting

Jet Grout Pileet Grout PileGeoEng Consultants (S) Pte Ltd


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SINGLE,DOUBLE & TRIPLE FLUID/TUBE JET GROUTING



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Typical Jet Grouting Parameters

Singapore Experience

Jet Grout Pileet Grout Pile

up to 4.5up to 2.0up to 2.50.5 to 0.8mIn Marine Clay

Size of Collumns

8 -125-105-10rpmRotation Speed

166 -1 28 - 30variesmin/mWithdrawal Rate

Lift ing Parameters

2 - 2.50.8 - 1.00.9 - 1.40.9 - 1.4W:CWater / cement

Cement and Grout

7 -127 -127 -12NAbarsAir Shroud Jet

300-400100-200200-400200-300barsGrout Jet

NA350-400NANAbarsWater Jet

Fluid pressures

175-500175-500175-500NAcfmAir Shroud Jet

60080-16060-20060-70l/minGrout Jet

NA60 -120NANAl/minWater Jet

Flow Rates

Super

Jet

Triple

Tube

Double

Tube

Single

TubeUnitParameters



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Jet Grouting

Diameter of columns formed 1.0m to 4.5mdiameter

The large diameters are formed by highgrout flow.

Diameter of rods approx 90mm to 120mm


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Believe Strength of Grout columns cannot be

ascertained mathematically

Large diameters = Large pressures Large pressures = Large movements

Large wall movements = Damage


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Strength Design of Jet Grouted Marine Clay

Most commonly jet grouted soil in Singapore is in

marine clay.

Strength of jet grouted marine clay can be estimated by

determining the various contents of clay soil, water and

cement.

The relative amounts of the three constituents in the jetgrout can be estimated by mass balance.

Refer: Lee Y. (1998)Refer: Lee Y. (1998) A Framework for the Design of Jet Grout Piles in Singapore MarinA Framework for the Design of Jet Grout Piles in Singapore Marinee

ClayClay.. MEngMEngThesis, Civil Engineering, NUS.Thesis, Civil Engineering, NUS.

Jet Grout Pileet Grout Pile


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Believe Large diameters = Large pressures

Large pressures = Large movements

Large wall movements = Damage

Strength of Grout columns cannot be

ascertained mathematically


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Distance from nozzle

PQ

air

shroudedno air

shroud

Energy decay of submerged jets


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Water jet impinge on soil wall.

Pore pressure increases rapidly in soil mass. Bonds between soil particles overcome by pore

pressure.

Soil particles disintegrates.

Therefore, ease of disintegration depends on

particle to particle bond.

Jet Grouting



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High pressure water jet impact on marine clay sample : note the total

disintegration i.e. no pieces of intact clay (LeeYeong 1998)



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WATER JET CUTS SOIL (NOT PUSH)



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CASE STUDY

Fill

UMC

F1/F2

LMC

OA

RL 86.0 JGP top

RL 82.0 JGP bottom

RL 86.5

RL 103.5

TYPICAL SECTION

Diaphragm wall 1.2m thick

Grout thickness 4m to 5m

Cu= 300kPa

E= 150 MPa


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IW 3 IW 4

2


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27th Dec 2007

IW 3 IW 42

Approx 6m width

Time vs Displacement

-400

-300

-200

-100

0

100

0 30 60 90

No of Days from 1st Dec

M

axinclinometer

displacements

IW 4 IW 3

th


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27th Dec 2007

3rd Jan 2008

IW 3 IW 42

Approx 6m width


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-400

-300

-200

-100

0

100

0 30 60

No of days from 1st Dec

Maxinclinometer

displacements

IW 4 IW 3

Inclinometer Records for IW3 and IW4

Jan 1st Feb 1st

Introduction of relief wells


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IW 4IW 3

7th Jan 2008


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-400

-300

-200

-100

0

100

0 30 60

Time from 1st Dec

Maxinclinometer

displa

cements

IW 4 IW 3

Inclinometer Records for IW3 and IW4

Jan 1st Feb 1st

Introduction of relief wells


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0

5

10

15

20

25

30

35

40

45

50

55

60

-400 -300 -200 -100 0 100 200 300 400

DEPT

H

(m)

Fill

UMC

F2

LMC

OA

RL 86.0

RL 82.0

RL 86.5

RL 103.5

Typical wall movement

mode


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Drilling to the point

Of Soil Improvement

When soil

improvement

commence slurry is

discharged

Start of volume build

up in cavity causing

heave or lateral disp

If annulus is

notmaintained

Discharge is

minimised

Causing

increased

ratio of soil

to cementand water to

cement


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Flow of slurry out of casing


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Jet Grouting Grout pressures are not the main cause of

wall movements. Wall movements can be controlled by

allowing slurry to be discharged

Relief wells at the location of each grout

point would be best

Controlled grouting volume is required


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Jet Grouting Avoid relief wells away from the point of

installation Relief wells need to be cleaned

If volume of grout is mixed with the slurry,the strength would be reduced

If proper relief wells are provided, chances

are the volume of cement can be reducedallowing some savings


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Grout Mixed Pile/Deep Soil Mixing/

Deep Cement Mixing



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Grout Mix Pile



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Grout Mix Pile


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Grout Mix Pile


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Grout Mix Pile


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Typical three shaft system


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Typical DSM/DCM/GMP parameters

Single double- triple-quadruple shafts Diameter of columns up to 2000mm per shaft

leading to approx 3.5m2 treated area per 4 shaftconfiguration (0.8m per shaft)

Strengths up to 1MPa in MC

Can be used for stiff soils depending on themachine torque

Pressures applied are slightly higher than thatrequired to over come the overburden pressures


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Typical DSM/DCM layout

- four shafts


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Enhanced GMP/Jet & Mechanical

Mixing


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Jet MechanicalMixing


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Enhanced GMP/JMM Similar to GMP/DSM/DCM

With the addition of a jet nozzle to cater forlarger diameter

A cross between the jet grout method and

the GMP/DSM/DCM methods

Used for wide ranged of soil types


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g


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nhanced GMP


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nhanced Grout Mixed Piles


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TYPICAL EGMP/JMM LAYOUT


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TYPICAL EGMP/JMM LAYOUT

Blade diameter

Diameter by

Jet pressure


-DCM/DSM/EGMP/JMM


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DCM/DSM/EGMP/JMM

Design Stage


Performance of grouting methods

Behaviour of Earth Retaining Structures during

Excavation

Construction Stage

Quality of grout cores

Properties of soils which have been disturbed

Heave and lateral movements of the Earth

Retaining Structures

CPT-1

QC (Mpa)

Change of soil properties

due to Deep Mixing Methods


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0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

0 2 4 6 8 10

Depth(m)

Fill

UMC

F2

LMC

OA

GL

CPT-5

QC (Mpa)

GL

Change of soil properties

due to Deep Mixing Methods


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0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25

D

epth(m)

Fill

MC

OA

GL


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DSM/DCM Method of grouting can cause disturbance

to existing soil layers. Wall movements could be larger than

predicted if the lower strengths are not

considered

Controlled grouting at the upper layers

may be required


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DSM/DCM More analysis and tests required to

understand the sensitivity of the variousgrouting methods

Wall stiffness may be a variation that

needs to be considered

Mixing of soft clays can cause it to be

remoulded sensitivity of Singapore

Marine Clay is about 5.



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Design Stage


Performance of grouting methods

Behaviour of Earth Retaining Structures during

Excavation

Construction Stage

Quality of grouting cores

Heave and lateral movements of the Earth

Retaining Structures

Performance of Earth Retaining Structures during

Excavation

Correlation of SPT N with UCS or Cu


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Occasionally we see CPT as a testrequirement.

CPT can only provide the determination of

the top of grout layer

Strength of soil improvement not

obtainable

Co e a o o S UCS o Cu



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Very often we see SPT and Coring tests tobe carried out in specifications

Core strength is commonly mentioned but

not N value to achieve So consultants/contractors treat it as clay

and use Cu= 5-6N

So to achieve 300kPa, we need nearlySPT N of 50 to 60



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Plot of Cu to SPT 'N' Values of Jet Grouted Areas

y = 0.0167x

0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3

0 20 40 60 80 100 120

SPT 'N' Value

UndrainedShearStrength,

Cu(N/mm

2)



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More data and statistical analysis needed to becarried out to allow a better representation ofSPT N

SPT N and coring methods of obtainingstrength have their own pit falls and data should

be carefully analysed.

Care has to be taken to ensure that the soil type

is considered in any analytical model

Discussions


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Grouting of soils is still considered an Art

as opposed to being a science

Grouting in soils seems to be still the

domain of specialist sub contractors

Consultants always would like to leave theissues to the contractors

Discussions


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More research and conscientious grouting works

is still required for more systematic grouting

procedures to be developed

Jet grouting is known to cause movements to

earth retaining structures if not done correctly

soil mixing methods remoulds the upper soil

layers and causes strength reduction and needsto be considered at design stage

Moving Forward


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g

More needs to be done to mitigate

movements caused by JGP. This has tobe part of the MS and trial test process

Present Advisory notes require criticalcontrol levels to be developed for grouting.

How do we do that if we are unsure of the

process?

Moving Forward


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g

For all grouting methods, more data

collection still required for a betterunderstanding of grouting strengths etc.

Contractors and Consultants need to workmore closely to have a better

understanding of the grouting methods


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Thank you

concerns on grouting in soils

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