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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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
Grouting of soilsrouting of soils
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Soil improvement for tunnelling
Grouting of soilsrouting of soils
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Underpinning
Grouting of soilsrouting of soils
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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
Grouting of soilsrouting of soils
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
Jet Grout Pileet Grout PileGeoEng Consultants (S) Pte Ltd
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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
Jet Grout Pileet Grout PileGeoEng Consultants (S) Pte Ltd
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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)
Jet Grout Pileet Grout PileGeoEng Consultants (S) Pte Ltd
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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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Time vs Displacement
-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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Time vs Displacement
-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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Jet Mechanical Mixing
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g
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nhanced GMP
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Jet Mechanical Mixing
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
Concerns of grouting
-DCM/DSM/EGMP/JMM
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DCM/DSM/EGMP/JMM
Design Stage
Strength and Stiffness
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.
Concerns of grouting
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Design Stage
Strength and Stiffness
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
Correlation of SPT N with UCS or 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
Correlation of SPT N with UCS or Cu
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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)
Correlation of SPT N with UCS or Cu
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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
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