Liquefaction and reliquefaction resistance of saturated sand deposits treated with sand compaction piles

To mitigate liquefaction and its associated soil deformations, ground improvement techniques were adopted in field to reinforce saturated sand deposits. Sand Compaction Pile (SCP) is one such popular proven treatment to improve liquefaction resistance of sandy deposits. Installation of sand compaction piles improves soil density and rigidity which further enhance seismic resistance against liquefaction and this was well evident from past field observations. However, studies involving SCP performance during repeated shaking events were not available/limited. In this study, using 1-g uniaxial shaking table, a series of shaking experiments were performed on SCP treated and untreated sand deposits having 40% and 60% relative density subjected to repeated incremental acceleration loading conditions (i.e., 0.1-0.4 g at 5 Hz frequency). Parameters such as improvement in soil resistance and relative density, generation and dissipation of excess pore water pressures, maximum observed foundation settlement and soil displacement and variation in cyclic stress ratio were evaluated and compared. Seismic response of liquefiable sand deposits was found to be improved significantly due to SCP installation together with occurrence of continuous soil densification under repeated loading. The experimental observations suggested that SCP can perform better even at repeated shaking events.