Grouting

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GROUTING

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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.

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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Grout Characteristics

•Groutability

•Stability

•Setting time

•Permanence

•Toxicity

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 fastRate of injection of a grout depends on

Viscoity of the groutPermeability of soilShear strength of soil

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Desirable properties of grout

Suitable viscosityHigh Viscosity for Coarse and Moderately

Permeable soils Low Viscosity for Fine grained soils of low

permeabilityCorrect setting timeMax. Volume with minimum weightStrengthStabilityDurability

Groutability Ratio

D15 = Particle size at which 15% of the soil is finer

D85 = Particle size at which 85% of the grout is finer

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85

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GroutD

FormationDGR

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StabilityCapacity of grout to remain in a fluid state and not

segregate into separate componentsSetting 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

PermanenceResistance the grout possesses against being

displaced from the soil voids with timeToxicity

Capacity of grouts to contaminate the grout water coming in contact with it.

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

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

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

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

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

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

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

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

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

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

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Grouting Plant for permeation grouting

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

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

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Systems of jet grouting

Sequence in Single Jet Grouting

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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)

Triple Jet Grouting Method

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Schematic diagram for Triple Jet Grouting

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Applications of Jet Grouting

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Groundwater control

Movement control

Support

Environmental

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

Movement Control

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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

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

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

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.

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.

Electrokinetic Injection

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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.

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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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Grouting arrangements Curtain grouting

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Blanket grouting

General Applications of Grouting

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Seepage Control For making vertical seepage barriers beneath

hydraulic structuresStoppage 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

Using soil fracture grouting 66

Grouting

Engineering

Transcript of Grouting