Expansive clay is a clay soil that is subject to large volume changes that are directly related to changes in water content
Soils are composed of a variety of materials, most of which do not expand in the presence of moisture.
However, a number of clay minerals are expansive. These include:smectite, bentonite, montmorillonite, beidellite, vermiculite, attapulgite, nontronite, and chlorite.
Sand Drain System Two types of sand draines are installed: displacement system and replacement system. A closed mandrel is driven into the design depth and the construction is completed by filling the sand into the cavity through the mandrel for the displacement system.