Aspects of sand behaviour by modified constant shear drained tests

Constant shear drained tests (CSD) are probably the most suitable to simulate the strength and deformation behaviour of soils in slopes under water infiltration conditions or lateral stress relief. This is significant because soil behaviour following a CSD stress path could differ from that of traditional compression triaxial tests. In this paper, CSD tests on sand following an alternative procedure are presented and discussed. The modified CSD tests were conducted by increasing the pore water pressure at a constant rate from one end of the specimen with water free to drain from the opposite end. Among the results from specimens consolidated at variable initial void ratios and principal stress ratios it was revealed that specimens showed a tendency to dilate even for loose sands; failure was reached at low axial strains; and a pre-failure type of instability could be identified. The modified procedure has the potential to provide new insights into the failure mechanisms of slopes under a water infiltration condition.