Experimental Study of Effect of Wetting-drying Path on Small-strain Shear Modulus of Silt

Abstract

Natural soils are usually under unsaturated state, especially soils at shallow depths below ground. The small-strain shear modulus of unsaturated soil is an important parameter for predicting ground deformation and dynamic responses of earth structures. Bender element tests were carried out on unsaturated compacted silt triaxial specimens to investigate the effects of suction and wetting-drying on small-strain shear modulus. Test results show that the small-strain shear modulus anisotropy of unsaturated compacted silt is negligible. The small-strain shear moduli G0(vh), G0(hh) and G0(hv) all increase with suction nonlinearly. For specimens under same suction but along different wetting-drying paths, their saturation degrees are different. Small-strain shear moduli decrease with increase of saturation degree. These observations are mainly due to the changes of average skeleton stress and meniscus water effect. Semi-empirical equation for describing small-strain shear modulus of unsaturated soil is modified based on test results; the effects of suction and saturation degree are both considered.