Liquefaction of sand under monotonic and cyclic shear conditions: Impact of drained preloading history

Abstract In-situ sand deposits inevitably undergo a preloading history caused by factors such as overlying structures, adjacent construction work, or repeated sedimentation and erosion; this will in turn affect their mechanical behavior and liquefaction susceptibility during subsequent loading. An experimental program was developed to explore the potential influence of the drained preloading history on the undrained response of sand subjected to both monotonic and cyclic loadings. The results indicate that the shear strength, dilatancy, and stiffness characteristics in monotonic tests depend on the relative directions of the drained preloading and subsequent undrained shearing. Two typical types of behavior are observed and identified in the cyclic tests, i.e., cyclic mobility and residual deformation accumulation failure, depending on the stress state prior to the undrained cycling. The cyclic resistance is quantified based on a failure criterion defined in terms of the triggering of flow behavior, and it is compared to that determined using a criterion of specified strain threshold. In particular, the direction–wise (compressional or extensional) influence of the preloading history on the liquefaction resistance and pore pressure generated in sand during cyclic loading agrees well with that observed during monotonic loading. Furthermore, a correspondence between the cyclic and monotonic tests can be derived, and a unified approach is proposed to evaluate both the monotonic and cyclic responses, irrespective of the drained preloading history.