CHARACTERIZATION OF EXPANSIVE SOILS

Most expansive soils encountered in engineering problems are at a degree of saturation below 100 percent. Knowledge of the moisture condition of such soils is best obtained by measuring soil suction. Soil suction can be determined routinely by using either the thermocouple psychrometer or filter-paper methods. The volume response can be characterized by obtaining a volume-change measurement along with a determination of suction change. This measure of soil response is called the suction compression index and is a fundatimating the suction compression index from index tests is provided. The soil stiffness, or the reduction in swell behavior caused by loads, must also be accounted for in making heave predictions. A nondimensional equation is presented that was developed by regression techniques from a large number of data found in the technical literature. The equation provides a tool for reducing the volumetric response of expansive soils as applied loads are increased. The use of this information in predicting heave is illustrated.