Anisotropic Lateral Pressures in Expansive Clay at Different Saturation and Compaction Levels

Abstract Lateral swelling pressure induced in expansive soils upon wetting can adversely impact the performance and integrity of earthen structures and foundations. Various laboratory testing techniques have been used in the literature to measure the lateral swelling pressure in expansive soils. However, most of these tests are performed under either constant-volume conditions or isotropic loadings, which cannot fully capture the lateral swelling characteristics of expansive clays. The main objective of this study is to investigate the development of lateral pressures and deformations in expansive clay at different saturation and compaction levels under anisotropic conditions. For this purpose, a new testing apparatus is built to measure both lateral and vertical components of the earth pressure while allowing volumetric changes in an anisotropic condition. The anisotropic state was achieved by letting the sides of the sample and the top move freely. The testing box was instrumented to measure soil moisture, temperature, suction, and lateral and vertical earth pressures versus time. The testing apparatus was used to investigate the effect of compaction level on lateral pressure, an effect that is not well examined in the literature. Test samples from an expansive clay collected from central Arkansas were compacted at different levels (85, 90, 95, and 100 % of Standard Proctor) and tested to measure lateral and vertical pressures as well as lateral deformations developed upon saturation under no surcharge conditions. The study used no surcharge to isolate the swelling pressure induced by moisture changes due to surface infiltration. Results show that the higher the compaction, the higher the lateral pressure. In contrast, compaction was found to have an insignificant effect on the vertical pressure at a compaction level of less than 90 %.