Effect of DSM Grids on Shear Stress Distribution in Liquefiable Soil

摘要

Site improvement by Deep Soil Mixing (DSM) to form in-ground shear walls has been used to remediate against the potential effects of earthquake-induced liquefaction. The grid pattern of soil-cement walls act as a confined shear-box which can provide additional shear stiffness and strength for sites to withstand strong ground motion. Current design practice for DSM grids commonly relies on the strain compatibility assumption, wherein the DSM walls and confined loose soil are assumed to experience the same shear strain. In this paper, the distribution of shear stresses and strains in liquefiable soil deposits treated with DSM grids are investigated using 3-D linear elastic finite element analyses of unit cells with the OpenSeesPL platform. From the analyses, it is found that the assumption of shear strain compatibility can be unconservative because portions of the DSM system can deform in flexure and the shear strains within the enclosed soil can exceed those within the DSM walls. The effects of input motion frequency content, wall stiffness, and area replacement ratio are evaluated. A revised design equation is proposed that accounts for the identified limitations in the strain compatibility assumption.