Geotextiles - are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. Typically made from polypropylene or polyester, geotextile fabrics come in three basic forms: woven (looks like mail bag sacking), needle punched (looks like felt), or heat bonded (looks like ironed felt). As the use of geotextile fabrics has expanded, geotextile composites have been introduced and products such as geogrids and meshes have been developed. Overall, these materials are referred to as geosynthetics and each configuration--geonets, geogrids and others--can yield certain benefits in geotechnical and environmental engineering design.
Deep Mixing/Mass Stabilization Techniques - These are essentially variations of in-Situ reinforcements in the form of Piles (as mentioned above) Blocks or larger Volumes. Cement, Lime/Quick Lime, Flyash, Sludge and/or other Binders (sometimes called Stabilizer) are mixed into the soil to increase bearing capacity. The result is not solid as concrete, but should be seen as an improvement of the bearing capacity of the original soil. The technique is most often applied on Clays or organic soils like peat. The mixing can be carried out by pumping the Binder into the soil whilst mixing it with a device normally mounted on an excavator or by excavating the masses, mixing them separately with the Binders and refilling them in the desired area. The technique can be used on lightly contaminated masses as a means of binding contaminants, as opposed to excavating them and transporting to landfill or processing.
Artificial Ground Freezing - While all types of soil and rock-containing moisture can be frozen, there has to be sufficient pore or joint water to achieve impermeability and increase in strength. Frozen conditions are created by circulating a cold medium through a series of freeze tubes positioned close enough together to form an ice wall, cofferdam or barrier. This wall will be virtually impermeable and the soil / ice structure will have greatly enhanced strength. Such properties are sought where linear structures have to be installed through very mixed soils with a high groundwater table. The effect is to produce a strong impermeable barrier so that work can proceed in dry conditions. Freezing is usually a temporary measure, with the groundwater regime restored after the thawing of the ice wall or barrier. It can be used permanently, however, in Arctic regions to maintain permafrost conditions beneath heated structures.
Artificial Ground Heating - Heating fine-grained soils to more than 100Â°C causes drying and strength gains, if re-wetting is prevented. It is a temporary measure. Heating from 600Â°C to 1000Â°C gives a permanent increase in strength and decreases the soil's swelling capacity and compressibility Heating the ground to a temperature high enough to cause the necessary changes in soil properties is achieved mainly by the infiltration of compressed, heated air. Alternatively, it can be an effect of the incandescent products of combustion through the soil pore. The process is dominated by two factors: the vaporisation of water on heating above 100oC, and the groundwater flow in and out of the zone being treated. Soils must be permeable to gas to allow removal of water vapour. Temperatures must be kept below soil fusion to prevent pore blockage.