Comparison of three inclusions in reducing lateral swelling pressure of expansive soils

Abstract

Lateral swelling pressures of expansive soils impose significant threats to the stability and safety of retaining structures. Placing a layer of compressible material, such as cohesive non-swelling soil (CNS), expanded polystyrene (EPS) geofoam or cohesionless soil (such as sand), between the retaining structure and the expansive soil can effectively reduce the lateral swelling pressure acting on the retaining structure. The work presented in this paper compares the efficiency of CNS, EPS and sand inclusions in reducing the lateral swelling pressure of a natural expansive clay. A special consolidometer was used to measure the lateral swelling pressure of expansive soil samples with and without inclusions under constant-volume condition, upon saturation. An analytical approach was used to interpret the efficiency of CNS, EPS and sand inclusions in reducing the lateral swelling pressure. It is found that (i) the efficiency of EPS inclusions is much higher than that of CNS and sand inclusions and (ii) sand is more effective than CNS in reducing the lateral swelling pressure at the same degree of compaction. It is suggested that EPS is preferred, the efficiency of sand is limited, and highly compacted CNS is unfavorable in reducing lateral swelling pressures.