Hi Rk, usually proctor compaction test (moisture-dry density relationship test) is carried out on the soil samples from the site to determine the optimum moisture content (OMC). Then field compaction needs to be organised to compact the soils at the moisture content of plus or minus 1% of OMC. But, if the soil is black soil or expansive clay (where plasticity is greater than 15), then it needs to be stabilised first or removed & replaced with better quality soil.

Dr Sinnappoo (Ravi) Ravindran thank you for your contribution to the discussion

The method of compaction is primarily of four types such as kneading, static, and dynamic or impact and vibratory compaction. Different type of action is effective in different type of soils such as for cohesive soils; sheep foot rollers or pneumatic rollers provide the kneading action. Three stages are included in the compaction process those are filling or packing, compaction and ejection. During the compaction process, if the loading pressure is increasing straightly, the powder assembly will experience three stages. Controlled Modulus Columns (CMC), also called rigid inclusions, are a ground improvement technique. They are used to control and reduce settlement and increase bearing capacity in soft or loose soils. Ground improvement is carried out for various objectives: to improve bearing capacity and reduce settlement of soft ground, prevent earthquake liquefaction, control groundwater, stabilize excavation bottom, prevent deformation of surrounding ground, or clean up contaminated ground. It is a simple ground improvement method, where the soil is compact through external compaction effort. Soil compaction is the process of applying external energy to a loose soil to consolidate it and remove air voids from the soil and thereby improving the physical properties of the soil. Types of Ground Improvement Techniques: Replacement of poor in-situ sub-soil, In-situ soil densification, Pre-compression / pre-consolidation of in-situ soil, Injections and grouting into in-situ soil, In-situ soil reinforcement and Uses of admixtures. As the moisture content increases, the water lubricates the soil, allowing it to move more easily into a compact state and the density increases. The effect of water content on the compaction of soil can also be explained with the help of electrical double layer theory of clay particles. The dry density increases as the added moisture lubricate the soil particles and enable greater compaction from the same applied energy. Once the optimum moisture content is exceeded, the water starts to displace the soil in a given volume, and the dry density decreases. The effect of increasing the amount of compactive effort is to increase the maximum dry density and to decrease the optimum water content (OMC). The compaction of soil increases with the increase in amount of compactive effort. With increase in compactive effort, the optimum water content required for compaction also decreases. At water content less than the optimum, the effect of increased compaction is more predominant.