Effects of Principal Strain Direction and Intermediate Principal Strain on Undrained Shear Behavior of Sand.

Anisotropic characteristics of granular soil consolidated to various initial stress states were evaluated under generalized strain paths using hollow cylinder torsional shear tests. Fraser River sand samples prepared by water pluviation were subjected to isotropic and anisotropic consolidation stresses, and sheared undrained along strain paths with constant intermediate principal strain parameter and various principal strain directions. Anisotropic stress response and stress-strain trends were examined by controlling the orientation of principal strains (αε) with respect to the depositional axis. A decrease in strain hardening tendency is observed as the major principal strain rotates towards the bedding plane. Considering different levels of anisotropic consolidation stresses also allowed a detailed examination of how initial static shear affects the responses. In particular, generated principal stresses and their directions, as well as the pore pressure responses, were closely examined. Novel findings are presented on the range of intermediate principal stress parameters (bσ) associated with the undrained plane strain condition where a value of bσ in the range of 0.2–0.4 was found to correspond to plane strain conditions. [ABSTRACT FROM AUTHOR]