Energy-Based Approach to Quantify Cyclic Resistance and Pore Pressure Generation in Anisotropically Consolidated Sand

In practical engineering, sand fills or deposits are often under an anisotropic stress condition. Thus, these soil elements sustain an initial static shear stress before being acted upon by cyclic loading because of traffic, waves, and earthquakes. To experimentally explore the effect of consolidation condition on the undrained cyclic response of saturated sand, a series of triaxial tests were performed on both loose and dense samples under varying consolidation conditions. The results indicate that different densities and consolidation conditions lead to three distinct failure modes: flow liquefaction, cyclic mobility, and residual deformation failure. Given the presence of the limiting values of residual pore pressures, a pore pressure–based failure criterion was used to evaluate the cyclic resistance of sand. It was found that the consolidation stress condition affects the cyclic resistance differently in loose and dense sand. The concept of dissipated energy was then used to delineate the pore pressure development during cyclic loading, and the amount of energy dissipated in sand was closely correlated to its relative density, consolidation stress ratio, and cyclic stress ratio. Moreover, a unique relationship between the residual pore pressure and dissipated energy was obtained for both isotropically and anisotropically consolidated sand with varying densities and cyclic stress amplitudes.