soil stabilization

Soil Stabilization with Cement

The soil stabilized with cement is known as soil cement. The cementing action is believed to be the result of chemical reactions of cement with siliceous soil during hydration reaction. The important factors affecting the soil-cement are nature of soil content, conditions of mixing, compaction, curing and admixtures used. The appropriate amounts of cement needed for different types of soils may be as follows:

Gravels - 5 to 10%

Sands - 7 to 12%

Silts - 12 to 15%, and

Clays - 12 - 20%

Soil Stabilization using Lime

Slaked lime is very effective in treating heavy plastic clayey soils. Lime may be used alone or in combination with cement, bitumen or fly ash. Sandy soils can also be stabilized with these combinations. Lime has been mainly used for stabilizing the road bases and the sub grade. Lime changes the nature of the adsorbed layer and provides pozzolanic action. Plasticity index of highly plastic soils are reduced by the addition of lime with soil. There is an increase in the optimum water content and a decrease in the maximum compacted density and his strength and durability of soil increases. Normally 2 to 8% of lime may be required for coarse grained soils and 5 to 8% of lime may be required for plastic soils. The amount of fly ash as admixture may vary from 8 to 20% of the weight of the soil.

Soil Stabilization with Bitumen

Asphalts and tars are bituminous materials which are used for stabilization of soil, generally for pavement construction. Bituminous materials when added to a soil, it imparts both cohesion and reduced water absorption. Depending upon the above actions and the nature of soils, bitumen stabilization is classified in following four types:

Sand bitumen stabilization

Soil Bitumen stabilization

Water proofed mechanical stabilization, and

Oiled earth.

Electrical Stabilization of Clayey Soils

Electrical stabilization of clayey soils is done by method known as electro-osmosis. This is an expensive method of soil stabilization and is mainly used for drainage of cohesive soils.

Soil Stabilization by Grouting

In this method, stabilizers are introduced by injection into the soil. This method is not useful for clayey soils because of their low permeability. This is a costly method for soil stabilization. This method is suitable for stabilizing buried zones of relatively limited extent. The grouting techniques can be classified as following:

Clay grouting

Chemical grouting

Chrome lignin grouting

Polymer grouting, and

Bituminous grouting

Soil Stabilization by Geotextiles and Fabrics

Geotextiles are porous fabrics made of synthetic materials such as polyethylene, polyester, nylons and polyvinyl chloride. Woven, non-woven and grid form varieties of geotextiles are available. Geotextiles have a high strength. When properly embedded in soil, it contributes to its stability. It is used in the construction of unpaved roads over soft soils. Reinforcing the soil for stabilization by metallic strips into it and providing an anchor or tie back to restrain a facing skin element.

The Soil stabilization with cement, bituminous, lime stabilization, mechanical stabilization, grouting, and geosynthetics, thermal, electrical have a method of soil stabilization.

soil stabilization

This is the process that is used to improve the engineering properties of the soil and thus making the properties of the soil more stable.

When the available soil for construction is not suitable for the intended purpose then the soil stabilization is required.

The stabilization process includes drainage, reconsolidation, compaction, and restricted to the processes which alter the soil material itself for improvement of its properties. For the purpose of stabilization, a chemical or a cementing material is added to natural soil.

In the earth structures, soil stabilization is used to decrease the compressibility and permeability of the soil mass and to increase its shear strength.

The soil stabilization requires increases the bearing capacity of the foundation soils. But, the main use of stabilization is to improve the natural soils for the construction of the airport runway and highways.

Principles of soil stabilization

The soil stabilization uses for controlling the grading of aggregates. And soils the construction of bases and sub-bases of the airport runway and highways.

Method of soil stabilization

Mechanical stabilization

Cement stabilization

Lime stabilization

Chemical stabilization

Bitument stabilization

Electrical stabilization

Thermal stabilization

Stabilization by grouting

Geosynthetics

Mechanical stabilization

Mechanical stabilization is the process which uses to improve the properties of the soil by changing its gradation. A composite material obtained by mixing two or more types of natural soils and this composite material is superior to any of its components.

Sometimes the soils with fine particles remove and the soils with coarse particles add to achieve the desired grading. Mechanical stabilization also knows as granular stabilization.

Soil Stabilization with cement

The process of cement stabilization can be done by mixing. The portland cement and pulverized soil with water and the compacting the mix to attain a strong material. The material takes place by mixing soil and cement knows as soil-cement. The material becomes hard and durable structural material as the cement hydrates and develops strength.

Bituminous stabilization

The stabilization of bituminous does with asphalt as a binder. Asphalts uses as cut-back with some solvent such as gasoline.

Because the asphalts are too viscous to use directly. Asphalts require a long drying period when they use as emulsions.

For the bituminous stabilization, any type of inorganic soils which can be mixed with asphalt is suitable.

In the cohesionless soils, the soil particles together bind by the asphalt and thus serves as a cementing or bonding agents.

In the cohesive soil, the soil is protected by asphalts by plugging its void and waterproofing it. Asphalt helps cohesive soil to increase the bearing capacity and to maintain low moisture content.

Generally, the required amount of bitumen varies from 4 to 7 % by weight. The actual amount determines by trail.

Chemical stabilization

Portland cement, bitumens, or other cementitious materials, chemical stabilization meets many needs. In surface treatment, it supplements mechanical stabilization to make the effects more lasting. In sub-surface treatments. Chemicals may use to improve bearing capacity or decrease permeability.

Soil-cement, a mixture of Portland cement and soil, is suitable for subgrades, base courses, and pavement of road not carrying heavy traffic. When the bitument-soil mixture is extensively used in road and airfield construction and sometimes as a seal for earth dikes.

Hydrated or slaked, lime may sue alone as a soil stabilizer, or fly ash, portland cement, or also bitumens. Calcium or sodium chloride uses as a dust palliative, and an additive in the construction of the granular base and wearing courses for roads. The chemicals may use to fill the voids in the soils, to cement the particles, or to form a rock-like material.

Electrical stabilization

The electrical stabilization of clayed soils does by a process known as electro-osmosis. As a direct current pass through a clayed soil, pure water migrates to the negative electrode.

It occurs because of the attraction of positive irons that are present in the water towards cathodes. The strength of the soil considerably increases due to the removal of water.

They improve for drainage of cohesive soils. Incidentally, the properties of the soil also improve.

Grouting

Grouting stabilization method, stabilizers introduce from injection into the soil. It always does under pressure, the stabilizers with high viscosity are appropriate only for the soils with high permeability. These are not appropriate for stabilizing clays because the clay has very low permeability.

The grouting method is appropriate for stabilizing the disturbed. This method stabilized an area that is close to an existing building.

Thermal Stabilization

In the properties of soil thermal change causes a marked improvement. The thermal stabilization can do in by heating the soil and by freezing the soil.

When the soil heat than the water content of the soil decrease. Thus, Electrical repulsing between the clay particles decrease and the soil strength increase. When if the temperatures are increases to more then 100 C. Then the adsorbed water drive off and the strength of the soil further increase. When the soil heats at the temperature of 400 C to 600 C. Then some Irreversible changes occur which make then soil non-expansive and no-plastic. The clay colds coveted into aggregates.

When the interparticle repulsion increases then cooling causes a small loss of strength of clayed soils. However, if the temperature decrease to the freezing point, the pure water freezes, and the soil stabilize. Ice so formed to act as a cementing agent.

Geosynthetics

Geosynthetics are man-made materials which use to improve the soil conditions. The word geosynthetics derive from

Geo=Earth or soil+syntheritcs =man -made

Geosynthetics is defined as a planar product manufactured from a polymeric material that is used with soil, rock or other geotechnical-related material as an integral part.