The perpetual shearing of granular soils under low stresses using the stadium shear device

Abstract

The constitutive response of granular soils under indefinitely large shear deformation and low stress controls the dynamics of shallow landslides and offshore pipelines. Current testing devices, however, are either limited to small shear deformation or involve a non-uniform stress distribution across the sample being tested. This paper presents the development of an original stadium shear device (SSD) that is free from those issues. In the SSD, soil samples can deform perpetually within a closed stadium shaped container that is sheared continuously by a belt. The stress uniformity across the width of the device is validated using Discrete Element Method (DEM) simulations, which give insight into the relationships between the normal stresses acting on the material. The performance of the SSD is validated using experimental data obtained from tests on glass beads, which further disclose stress and void ratio relationship in soils. When applied to sub-angular natural sands with different degrees of polydispersity, the SSD reveals a weak rate hardening of friction coefficient and sample dilatancy that reaches the loosest possible density at critical state, regardless of the initial packing conditions.