Experimental Investigation on Shear Behavior of Partially Saturated Silty Soil under Constant Water Content and Constant Void Ratio Conditions

Abstract

Abstract Matric suction is a crucial parameter that affects how unsaturated soils behave in terms of shear strength. Understanding it is essential for solving geotechnical problems like the stability of unsaturated soil slopes, foundations, embankments, and retaining walls. To investigate the shear behavior in unsaturated soil, a double cell triaxial test apparatus is used in the current research to carry out a series of triaxial compression tests under constant water content and constant void ratio conditions. Samples of silty soil, named DL-clay, were prepared with three different degrees of compaction: 80 %, 83 %, and 86 %, and water contents of 20 % (optimum water content) and 25 %. The soil samples were consolidated isotropically under net confining pressures of 300 kPa and 500 kPa before being sheared with constant volume. In another series of tests, water was infiltrated into the sample at 0 kPa deviatoric stress before the start of shearing with constant volume. Some specimens were also sheared with constant confining pressure for comparison purposes. From the test results, it is ascertained that maintaining a constant volume, i.e., constant void ratio during shearing, gives contour-like trajectories that can aid in defining the state boundary surface of unsaturated soil. It was also observed that within the axial strain range of 0–2 %, there was unusual behavior of a temporary sudden dip in the axial stress, which was more perceivable for samples having a high value of initial matric suction.