Mechanism controlling the shrinkage limit of soils

Based on the results from an extensive experimental program involving a number of natural soils as well as pure clays with extreme clay mineral types, namely kaolinite and montmorillonite, as the principal clay minerals, a hypothesis explaining the mechanisms controlling the shrinkage limit has been proposed. The shrinkage limit of a natural soil has been shown to be primarily a result of the packing phenomenon, which in turn is governed by the grain-size distribution of the soil; the shrinkage limit of pure clays appears to be affected by the fabric also. Even though clay-sized particles play an important role in the shrinkage phenomenon, there is an optimum clay content at which the shrinkage limit of a soil can become minimum. It has been further illustrated that the shrinkage limit is not at all related to the plasticity characteristics of the soil. As the factors governing the shrinkage limit are entirely different from those controlling the swelling of soils, the shrinkage limit cannot indicate the swelling behavior of the soil