module 11:geomembranes, grouting and injection and...

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Module 11:Geomembranes, Grouting and Injection and Insitu Ground Reinforcement Lecture 33:Grouting and Grout Material

The Lecture Contains:

Grouting And Injection

file:///D|/Dr.patra/ground_improvement_techniques/lecture33/33_1.htm [10/12/2011 3:47:15 PM]

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Grouting, Grouting materials, Operations, Methods of Grouting, Guniting.

Definition It is defined as the injection of fluidized materials into voids of the ground or spaces between the ground and adjacent structures generally through boreholes and under pressure.

Categories of Grouting:

● Penetration grouting (intrusion, permeation) ● Displacement grouting.● Compaction grouting (including slab-jacking )● Grouting of voids ● Jet grouting (replacement)● Special grouting applications and techniques, including electro grouting.

Penetration grouting

Process of filling joints or fractures in rock or pore spaces in soil with a grout without disturbing the formation. It refers to the replacement of water in voids between soil, particles with a grout fluid at low injection pressure so as to prevent fracturing.

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Figure 33.1


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Displacement grouting: It is the injection of grout into a formation in such a manner as to move into the formation, it may be controlled, as in compaction grouting or uncontrolled. As in high pressure soil or rock grouting which leads to splitting of the ground, also called hydrofracture.

Figure 33.2

Compaction grouting: It is a very stiff (say 25-mm slump) mortor is injected into loose soils, forming grout bulbs which displace. and densify the surrounding ground, without penetrating the soil, pores.

Jet grouting: It is a technique where high –speed water jets emanating from a drill bit cut into alluvial soils: as the drill but is withdrawn grout is


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pumped through horizontal nozzles and mixes with or displaces the soil. The original foundation material is thus replaced with a stranger and/or more impermeable grout-soil mixture. Jet grouting may be used to form cut off walls, form a deep foundation.

Figure 33.3

Electro grouting: It is a term used for promoting electro chemical hardening during electro osmosis by adding chemicals, such as sodium solicate or calcium chloride at the Anode. Under the influence of, the electric field, these chemicals permeat the ground, flowing in the direction of Cathode, while the Anode becomes a grout injection pipe.


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Grout Materials:

1. Suspensions:

Small particles of solids are distributed in a liquid dispersion medium. Example: cement and clay in water

2. Emulsions:

A two phase system containing minute (colloidal) droplets of liquid in a disperse phase. Example : bitumen and water.

Foams created by emulsifying a gas into the grout material, which could be cement or an organic chemical. Foaming agents increase surface tension; assist in forming bubbles by agitation.

3. Solutions: Liquid homogeneous molecular mixtures of two or more substances. Example: sodium silicate, organic resins, and a wide variety of other so called chemical grouts.

Principal type of Grout:State

Suspensions Liquids

Aerated emulsionsUnstable Stable Chemical

products

Grout type CementBentonite + cement

Deflucculate bentonite

Sodium silicate hard gels

Sodium silicate diluted gels

Organic

resins

cement foams

Organic foams

Range of uses Fissures Sand and Gravels k m/s CavitiesHigh water

flows

>5 >

> > >

Grouting| control Refusal

pressure Limited Quantities Filling


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Relative cost for the products to

fill 1 voids

4.2 (deposite) with

1 (cement 200kg, betonite 30kg)

0.8 -1 6 2.4 10-500 1.2 10

Figure 33.4


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The relationship between the expansion coefficients and air ratio is analogous to that of void ratio and porosity of a soil.

Permanency: The resistance against mechanical deterioration due to freeze thaw or wetting and dry cycles and chemical degradation by reaction with ground water or soil constituents.

Toxicity: It refers to health hazards in handling the grout and its effects on the quality of the ground water it is in contact with.

Rheology of Grouts It is the study of flowage of materials.

Basic Rheological Properties: Important basic characteristic of grout are stability, setting time and viscosity

Stability:

A grout is referred to a stable, if its particles remain in suspension of solution until it has reached the destination in the ground. The breaking of an emulsion and exudation of liquids from colloidal gel could also be considered a sedimentation process.


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Grouting and Injection

Setting time: Time required for the grout to harden cement based grouts normally set within 4 to 24 hr, depending on the additive used.

Viscosity( :-

It is defined by Newton’s law of viscosity as the proportionality factor relating the shear resistance

in a fluid to the velocity gradient which represents the rate at which one layer of fluid moves relative

to an adjacent layer.

It is valid for laminar flow. It is called dynamic viscosity.

For turbulent flow:

Turbulent flow is important as far as maintaining the stability of grout during pumping is concerned.

Measurement of viscosity:

By viscometer


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Figure 33.5

Inner cylinder is stationary and the outer rotates.

Where T= torque, Nm


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Grouting and Injection

On a construction site a check of viscosity of a grout can be obtained by measuring the time required for a certain amount of fluid to flow through a standardize tunnel. The time recorded is usually for the out flow of the first 1000 ml.

Figure 33.6

Ideally, a grout should have low viscosity a controllable setting time and high strength once it is in ground. In addition it should be nontoxic, permanent and cheap.

Bingham fluid:

The rheological behavior of a Bingham fluid is expressed by


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Figure 33.7

Flow behavior of equation describes as ideal plastic.

Water Newtonian fluid

Clay in suspension non-Newtonian fluid

A clay or cement grout may be approximately treated as a Bingham Body .


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Stability:



module 11:geomembranes, grouting and injection and...

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