Cyclic Rotational Simple-Shear Behaviour of Sand-Steel Interfaces

Abstract

ABSTRACT A series of two-way cyclic tangential-displacement-controlled tests and cyclic rotational tests were carried out to study the behaviour of an interface between a dry silica sand and a rough steel plate. A recently developed interface apparatus, C3DSSI, was employed to perform the experiments. The sand container in C3DSSI is a simple shear box which allows the tangential displacements due to the shear deformation of the sand mass to be distinguished from the sliding displacements at the interface. The tangential forces are applied to the interface plane through an X-Y loading table by using two ball screw stepper motors. The elliptical and circular rotational paths on the interface plane are generated by combining the sinusoidal tangential-displacement-controlled cycles produced simultaneously in the x- and y-directions. A pneumatic actuator which is controlled by a motorized regulator induces the normal stress on the interface. The results of two-way displacement controlled cyclic tests indicated that the interface may fail and strength reduction may occur, even at tangential displacement amplitudes less than that required to mobilize the peak strength in a monotonic test. The results of cyclic rotational tangential displacement paths showed that by approaching a full circular path from an elliptical path the average compression of the sand mass increased for the same number of cycles. The peak and residual strengths, however, reduced as the displacement path became a circle.