Undrained cyclic behavior of rubber-sand mixture under multi-directional loads

The undrained cyclic behavior of rubber-sand mixture (RSM) is usually investigated under cyclic loads with unidirectional shear stress. However, bidirectional shear stress exists in many engineering practices subjected to complex loads, under which the liquefaction resistance of soil may be overestimated. Furthermore, the soil behavior under bidirectional shear stress exhibits quite differently from that under unidirectional shear stress. Therefore, undrained cyclic behavior of RSM under bidirectional shear stress should be further investigated. In this study, several specimens made by RSM with different rubber contents (from 10% to 30% by volume) are consolidated under two conditions, K0 consolidation and the combination of K0 consolidation with consolidation shear stress (CSS). Subsequently, numerous tests are conducted under the unidirectional and bidirectional cyclic loading paths to investigate the cyclic undrained behavior of RSM. The results show that the bidirectional shear loads incur a larger normalized pore water pressure (PWP) than unidirectional shear loads. In addition, an energy-based method is employed to understand the relationship between cumulative energy and normalized PWP. During the stage of rapidly accumulating PWP, the dissipated energy required to generate the same normalized PWP is identical, and it is independent of the shapes of loading paths.