Cyclic behaviour of an unsaturated silty soil subjected to hydro-mechanical damage

Department of Civil Engineering, Ashikaga University. Tochigi, Japan

^* e-mail: tomo@ashitech.ac.jp

Abstract

The dynamic behaviour of unsaturated soil subjected to cyclic loading is considered using two stress state variables, net normal stress and matric suction. Though the influence of excess pore-water pressures in fully saturated soils has been investigated through experimental works for decades, it is significant in practice for unsaturated soil dynamic behaviour to be compared to saturated soil dynamic strength-deformation properties. Matric suction can be described as a scalar, which is useful in establishing safety factors and in mathematical simulations. This study focused on the dynamic behaviour of unsaturated soil leading to liquefaction failure. Solving practical problems requires considering the properties of unsaturated soil subjected to creep before introducing dynamic loading effects. This testing program consisted of a creep test and a cyclic loading test. Notably, a low suction range of soil structure is closely related to large deformations or leads to failure impacting the resistance of soil particle cohesion, including the macro-micro structure. Creep force was applied under lateral confining pressure, and suction measurements are indicating a gradual growth of excess pore-water pressure. Moreover, this study considered a dynamic triaxial compression test under the undrained condition for unsaturated soil with suction and creep history.