Liquefaction mitigation mechanisms of stone column-improved ground by dynamic centrifuge model tests

Abstract

Stone column is one of the prevailing liquefaction mitigation techniques to densify the surrounding soil, expedite the drainage and bring the possible shear reinforcement effect. The mitigation mechanisms of liquefaction triggering and the associated deformation of the improved ground have not been well explored yet, which hinders the development of robust design in engineering practices. Three centrifuge model tests, including a loose sand model, a dense sand model and a dense sand model with stone columns were conducted to explore the individual effect of densification and drainage caused by stone columns on seismic responses of a level silty sand ground, including the excess pore water pressure, acceleration and ground settlement, etc. The densification effect increases the dilatancy of the surrounding soil and hinders the generation of excess pore water pressure during shaking, thus significantly reduces the liquefaction potential and post-shaking settlement as well. However, it amplifies the upward propagating ground motion considerably. The drainage effect in a densified ground with SCs mainly takes place after shaking, and it accelerates the dissipation rate about 5–10 times that of a densified ground without SCs, which helps to quickly restore the ground stiffness and reduce the deformation to some extent. The contributions from the two effects to the post-shaking ground settlement were also observed and discussed. The present study provides insights on liquefaction mitigation mechanisms of the stone column-improved ground and valuable benchmark tests for further analysis.