ground improvement technique- grouting and its methods and applications

1. 1
GROUTING

2. 2
GROUTING
 Injection of a slurry or a liquid solution into a soil or
rock formation
 The grout subsequently hardens - increases the
strength and decreases compressibility and
permeability.

3. MODES OF GROUTING
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 Permeation or Penetration- Grout flows into soil voids
freely with minimal effect
 Compaction or Controlled displacement- Grout
remains more or less intact as a mass and exerts
pressure on soil
 Hydraulic Fracturing or Uncontrolled displacement-
Grout rapidly penetrates into a fractured zone created
when the grout pressure is greater than tensile
strength of soil or rock

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5. 5
Grout Characteristics
• Groutability
• Stability
• Setting time
• Permanence
• Toxicity

6. Groutability
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 To obtain satisfactory performance, grain size
distribution should be known because it shall show
the relationship between the grout particle size and
the void dimensions.
 Pumping pressure should not be large enough for
particles of soil to be disturbed.
 Grouting pressure is limited to 20 kN/m2
 Quality of a grout must be sufficiently fluid to enter
the soil quickly
 The movement should not be too fast
 Rate of injection of a grout depends on
 Viscoity of the grout
 Permeability of soil
 Shear strength of soil

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Desirable properties of grout
 Suitable viscosity
 High Viscosity for Coarse and Moderately Permeable
soils
 Low Viscosity for Fine grained soils of low
permeability
 Correct setting time
 Max. Volume with minimum weight
 Strength
 Stability
 Durability

8. Groutability Ratio
 D15 = Particle size at which 15% of the soil is finer
 D85 = Particle size at which 85% of the grout is finer
)(
)(
85
15
GroutD
FormationD
GR 
8

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 Stability
 Capacity of grout to remain in a fluid state and not
segregate into separate components
 Setting Time
 Time required for the grout to set into cemented mass
or gel
 Early setting causes difficulty in the grout reaching its
destination
 Late setting causes the grout being washed away if
seepage is occuring through soil
 Permanence
 Resistance the grout possesses against being
displaced from the soil voids with time
 Toxicity
 Capacity of grouts to contaminate the grout water

10. GROUT MATERIALS
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 Suspensions – Grout particles in suspension in a
liquid medium- Cement+ Water, Clay etc
 Emulsions – Minute droplets of liquid in
suspension- Asphalt or bitumen with water
 Solutions – Liquid homogenous mixture of two or
more materials- Chemical Grouts

11. SUSPENSION GROUTS-GROUTING WITH
SOIL
 GR > 20
 Soil can be used to fill up voids in coarse grained
soils
 Soil used as grout- very fine grained
 Clay grouts – to reduce permeability
 Kaolinite and Illite based clays – low viscosities –
filler grouts
 Bentonite – to control viscosity strength and flow
properties
 Mud jacking – to raise pavement slabs and to
underpin shallow building foundations

12. SUSPENSION GROUTS-GROUTING WITH
CEMENT
 Uitable for cracks or voids wider than 0.2 mm
 Usually formed from OPC and Water
 Water cent ratio – 0.5:1 to 5:1
 Rapid hardening cement – prefered in ground
with flowing water
 Super sulphated cement – for fissured rocks
 Admixtures such as bentonite used to keep the
cement particles in suspension
 Seepage cut off beneath dams, ground water
control

13. EMULSION GROUTS – ASFALT
EMULSION
 Anionic or cationic asphaltic globules are
manufactured by choosing proper emulsifying
agent
 The globules (1 to 2 µm dia) along with water
used as grout to fill soil voids and rock fissures
 Rock fissues of 10 µm size and medium silts can
be grouted
 Slow setting emulsions generally chosen – they
can travel longest distnce into the material

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SOLUTION GROUTS – CHEMICAL GROUTING
 Chemical grouts like silicates and acrylic resins
 Solidify by chemical reaction
 Seepage barriers, stabilisation of soils around
tunnels
 Principle of injection-permeation grouting

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16. GROUTING SYSTEMS- ONE SHOT & TWO
SHOT
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ONE SHOT
SYSTEM
All chemicals are injected
together after premixing
Setting time is controlled
by varying the catalyst
concentration according
to the grout concentration,
water composition and
temperature
TWO SHOT
SYSTEM
One chemical is injected
followed by injection of a
second chemical which
reacts with the first to
produce a gel which
subsequently hardens
This is slower and require
higher injection pressure
and more closely spaced
grout holes

18. Grouting Procedure
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Depending on the material to be grouted (Rock, natural
soil or fill), its quality and the purpose of grouting, a well
planned procedure has to be adopted to attain the
desired result
 Ground Investigation
 Grout Holes pattern
 Grouting Plant and Equipment
 Grouting sequence
 Grouting methods

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Ground Investigation
 Provides information regarding the ground- whether
it can be grouted or not
 Choice of grouts-type and amount
 Include a geological survey, Drilling boreholes,
Collection of samples for laboratory tests

20. Grout Holes Pattern
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 Based on the nature of work, the number of drill
holes, depth and pattern to be decided
 Follows a grid pattern such that radius of penetration
is sufficient to cause slight overlapping between
adjacent holes

21. Grouting Plant and Equipment
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 Measuring Tank – To control the volume of grout
injected
 Mixer – To mix grout ingredients
 Agitator – To keep solid particles in suspension until
pumped
 Pump – To draw the grout from the agitator to deliver to
the pumping line
 Control fittings – To control the injection rate and
pressure so that the hole can be regularly blend with
water and thin grout
 Piping connected to grout holes

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25. GROUTING SEQUENCE
GROUTING
FROM BOTTOM
A grout hole of 50 to 75 mm diameter is
drilled to full planned depth.
In rigid soils or in intact rock strata a self
expanding packer is placed directly above the
lowest zone and grout is pumped in.
The procedure is repeated after the packer is
raised and fixed to the next zone
Thus the drill hole is grouted successively
upwards
GROUTING
FROM TOP
Holes are drilled down to the seam closest to
the surface and grouting is carried out.
Holes are then cleaned by washing and
drilling continued to the next seam.
Grouting process is then effected.
Subsequent washing followed further drilling
and repeated grouting are done until the
entire operation is completed. [Fig. 6.11(a)]
Grouting is facilitated in a particular zone by
fixing packers on the top and bottom. [Fig.
6.11(b)]

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GROUTING METHODS
Permeation Grouting
Compaction Grouting
Jet Grouting
Soil Fracture Grouting
Circuit Grouting
Point Grouting
Electro kinetic injection

27. Permeation Grouting
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• Grout fills the pores without any volume
changes. Include Cement grouts, bentonite
grouts and chemical grouts.
• Grouting into an open hole in self-supporting
ground through pipes at the surface through an
injection pipe held in place in the hole or casing
by a packer.
• From a pipe driven into the ground and
withdrawn as injection proceeds
• Through a pipe left in place in the ground as with
a tube

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Permeation Grouting

29. 29
Grouting Plant for permeation grouting

30. Applications of Permeation
Grouting
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 Seepage Control
 For making vertical seepage barriers beneath
hydraulic structures
 Stoppage of seepage through joints of underground
structures such as tunnel lining/ basement wall, etc.
 Soil Solidification and Stabilization
 For stabilization of soil around tunnels and shafts

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Compaction grouting
 A good option if the foundation of
an existing building requires
improvement, since it is possible
to inject the grout from the side
or at an inclined angle to reach
beneath the building
 A bulb shaped grouted mass is
formed.
 Soil-cement grout
 Can be performed as
pretreatment before the structure
is built

32. Applications of Compaction Grouting
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 Densification of loose stratum
i) underlying dense soil
ii) beneath foundations or floor slab-slab jacking
 Filling of large underground cavities
 Densification of collapsible soils
 Densification of soils showing organic
degradation

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Jet Grouting
 Involves the injection of low viscosity liquid grout into
the pore spaces of granular soils. This creates
hardened soils to replace loose liquefiable soils
 Jet grouting is used as replacement technique, in which
soils ranging from silt to clay and weak rocks can be
treated
 This method consists of lowering a drill pipe into a 150
mm dia bore hole
 The drill pipe is specially designed which
simultaneously conveys pumped water, compressed air
and grout fluid.
 Three systems of jet grouting
 Single, Double & Triple

34. 34
Systems of jet grouting

35. Sequence in Single Jet Grouting
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36. Triple Jet Grouting
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 At the bottom end of the pipe two nozzles are
provided at 500 mm apart.
 The upper nozzle (1.8 mm diameter) delivers
water surrounded by a collar of compressed air to
produce a cutting jet.
 The grout is delivered through the lower nozzle (7
mm dia)

37. Triple Jet Grouting Method
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38. Schematic diagram for Triple Jet
Grouting
38

39. Applications of Jet Grouting
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 Groundwater control
 Movement control
 Support
 Environmental

40. Ground Water Control
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 Preventing flow either through the sides or into
the base of an excavation
 Controlling groundwater during tunneling
 Preventing or reducing water seepage through a
water retention structure such as a dam or flood
defence structure
 Preventing or reducing contamination flow
through the ground

41. Movement Control
41
 Prevention of ground or structure movement
during excavation or tunnelling
 Supporting the face or sides of a tunnel during
construction or in the long term
 Increasing the factor of safety of embankments or
cuttings
 Providing support to piles or walls to prevent or
reduce lateral movement

42. Support
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 Underpinning buildings during excavation or
tunnelling
 Improving the ground to prevent failure through
inadequate bearing
 Transferring foundation load through weak
material to a competent strata

43. Environmental
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 Encapsulating contaminants in the ground to
reduce or prevent contamination off site or into
sensitive water systems
 Providing lateral or vertical barriers to
contaminant flow
 Introducing reactive materials into the ground to
treat specific contaminants by creating permeable
reactive barriers

44. Circuit Grouting
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 Based on the principle
of grouting from the
top downwards.
 A drill hole is bored to
the depth of the
bottom zone and grout
is pumped down the
grout pile and returned
up the drill hole.

45. Point Grouting
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 In shallow work of 10 to 12 m deep the grout is
injected from the points of a driven or jetted
lance.
 Injections are delivered at pre-determined
positions along the line of drive and also on the
return in systems where a second reacting grout
ingredient is to be placed independently of the
initial injection.

46. Electrokinetic Injection
46
 Stabilization of silty soils may not be possible by
chemical or admixture perhaps because of lack of
confinement or the necessity to avoid disturbance
of the ground.
 Chemical stabilizers are introduced at the anode
and carried toward the cathode by electro-
osmosis.
 Direct current electrical gradients of the order of
50 to 100 Volts/m are required.

47. 47
Soil Fracture Grouting
 Root-like zones of grout material is formed in the
soil mass
 Sleeved pipe grouting technique is used
 Used for restoration of verticality of a tilted building

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49. 49
Grouting arrangements
 Curtain grouting

50. 50
 Blanket grouting

51. General Applications of Grouting
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 Seepage Control
 For making vertical seepage barriers beneath hydraulic
structures
 Stoppage of seepage through joints of underground
structures such as tunnel lining/ basement wall, etc.
 Soil Solidification and Stabilization
 For stabilization of soil around tunnels and shafts
 Vibration Control
 Chemical grouting through machine foundation soil will
alter the elastic properties of the soil and results in
increased rigidity of the base resulting in decrease of
amplitudes.

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Seepage Control

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Soil Solidification and Stabilization

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66. Using soil fracture grouting66