A Hollow Cylinder Torsional Shear Device to Explore Behavior of Soils Subjected to Complex Rotation of Principal Stresses

Geotechnical Testing Journal

Siva Sivathayalan, & Prasanna Rousseau

2021-05-03

A hollow cylinder torsional shear device that is modified to simulate more generalized earthquake loading, involving simultaneous compression and shear wave loading in situ, is presented. The nature and degree of stress rotation due to coupled action of compression waves and shear waves are discussed, and illustrative experiments conducted to simulate different loading scenarios in the laboratory are presented. The stress rotation due to this coupled loading is significantly influenced by the initial consolidation stress state and shearing parameters such as the ratio between shear stress and normal stress increments (ΔS/ΔN) and the phase shift (ϕ) between the waves. The representative (ΔS/ΔN) ratios were obtained from the numerical simulations and used in hollow cylinder torsional shear apparatus to investigate the cyclic response of Fraser River sand under the simultaneous action of normal and shear stresses. Typical cyclic test results demonstrating the capability of a hollow cylinder torsional shear apparatus commissioned at Carleton University in following complicated cyclic loading paths are presented in this paper. It is noted that loading under such nonconventional stress paths, such as elliptical and circular paths, could be initiated along different pathways. Cyclic test results along these pathways demonstrate that soil response is dependent on the overall path including the initial stress state. Test results also highlighted the significance of stress rotation and cyclic stress paths in affecting the liquefaction susceptibility of sands.