Monotonic and post cyclic behavior of sands under different strain paths in direct simple shear tests

Abstract

Engineering geological characteristics of soils have been developed based on the assumption of two limiting drainage boundary conditions: fully drained and fully undrained. In recent years, an increasing number of research works have been applied to study the effects of partially drained conditions on the behavior of soils. Different strain paths can be employed to analyze soil behavior, including limiting conditions. However, it is well known that the fundamental parameters of sands are dependent on the strain path that they experience; the post cyclic behavior of sand under different strain paths in plane strain conditions is not evaluated appropriately yet. In this paper, using a stack-ring type direct simple shear apparatus, the main characteristic parameters of Firoozkuh No. 161 medium sand are evaluated. Monotonic and post cyclic behavior of sand specimens under dilative, contractive, and constant volume conditions are compared. It is shown that the strain path significantly affects sand behavior. Achieved results demonstrated that slopes of steady-state lines in stress paths (asymptotic stress ratios) are dependent on the magnitude of partial drainage for both monotonic and post cyclic conditions, and the initial stress state of samples at the commence of post cyclic loading is an important parameter to define post cyclic behavior of sands under partially drained situations.