Effect of drainage conditions on the shear response of liquefiable sands: A DEM study

Abstract

In geotechnical design, it is often assumed that soil deforms in either a fully drained or undrained manner. However, in complex scenarios, evaluating a partially drained condition where volumetric changes and pore water pressures coexist becomes essential for a conservative design. Evidence from centrifuge tests in offshore systems suggests that drainage conditions are key to identify a critical design condition and to explain the deformation levels observed in liquefiable sites. This study investigates the effect of partial drainage conditions on the mechanical behavior of liquefiable sands using 3D DEM simulations. A set of virtual sand specimens is created by isotopically compressing representative samples of Toyoura sand with a specific interparticle friction value. The mechanical response of partially drained assemblies is simulated by applying a controlled volumetric strain condition to the DEM sample. The fully drained response is used to develop the strain control in the partially drained simulations. The coordination number and the deviatoric fabric are tracked along the stress path to examine the effect of drainage around the instability onset. Results indicate that partially drained shearing induces a controlled reduction in mean stresses and a contraction of the specimen in the early stages of shearing. Similar micromechanical features are observed between the partially drained and fully drained tests.