Post-liquefaction deformation mechanisms of stone column-improved liquefiable sloping ground under cyclic loadings

Liquefaction-induced large deformations in sloping ground caused heavy damage to buildings and infrastructures during earthquakes, and its evaluation and mitigation challenge. In this study, a series of soil element tests using hollow cylinder apparatus (HCA) were conducted to investigate the relationship between residual volumetric strain and residual shear strain of medium dense to dense saturated sand with moderate initial static shear stress. The soil element tests indicate that the developments of residual volumetric strain and residual shear strain are dominated by the Post-liquefaction Deformation Potential (PLDP) of soil, which is well correlated to the maximum cyclic shear strain developed during cyclic loading. Then, the applicability of PLDP to characterize the post-liquefaction deformation response in gently sloping ground was investigated by centrifuge model tests without and with stone column improvement. The model tests of medium dense and dense sand slopes proved the applicability of PLDP preliminarily. The mitigation mechanisms against settlement and lateral spreading in gentle slopes by densification and drainage effects induced by stone columns were also observed and discussed. The present study provides the conceptual term of PLDP for evaluating post-liquefaction deformations of natural and stone column-improved gently sloping grounds, which helps to develop mitigation techniques for liquefiable sloping ground subjected to earthquake loadings.

Automated summary

This study investigated the large deformations caused by liquefaction in sloping ground and the methods for evaluation and mitigation. Soil element tests and centrifuge model tests were conducted to study the relationship between residual strain and Post-liquefaction Deformation Potential (PLDP). The tests showed that the developments of residual strain were controlled by PLDP, which is correlated with the maximum cyclic shear strain. The applicability of PLDP was verified in model tests, and the mitigation mechanisms of densification and drainage induced by stone columns were observed.