Undrained Behavior of Sand–Structure Interfaces Subjected to Cyclic Torsional Shearing

Abstract

This paper presents results from an experimental study on the undrained behavior of sand–structure interfaces subjected to cyclic undrained torsional shearing. The goals of the study are to develop understanding of the response of sand subjected to cyclic torsional loading and to develop a theoretically sound and scale-sensitive framework for interpretation of results. The results characterize the effects of initial void ratio, confining stress, surface roughness, particle angularity, and imposed loading conditions (i.e., torsional versus axial shearing). The responses of all specimens subjected to torsional shear, including those prepared at high relative density, were dominated by contractive tendencies characterized by significant excess pore-water pressure generation. Mechanisms for excess pore-water pressure generation based on experimental evidence of local volume-change tendencies at various locations within the specimens are presented. Torsional interface shearing consistently generated pore-water pressures at faster rates than axial shearing, making the former more efficient for studying cyclic soil behavior. Implications of the results of this study on the deployment of a proposed soil characterization tool are discussed.