Addressing Influence of Prefabricated Vertical Drains in Liquefaction Resistance Under Multiple Shaking Events

Soil liquefaction and its associated ground failures during earthquake is one of the major potential hazards in recent years. The important aspect of geotechnical earthquake engineering is to mitigate liquefaction and its associated effects for assuring the safety of foundations. To mitigate liquefaction, there are different ground improvement techniques available and installation of prefabricated vertical drains is one such recently developed improvement technique which involves installation of PVDs for dissipating pore water pressures. The present study aims to evaluate the efficiency of prefabricated vertical drains reinforced ground subjected to repeated acceleration loading conditions. Shaking table tests were performed on poorly graded sand with varying ground density conditions subjected to repeated incremental acceleration loading with and without PVD system. For experimental investigations, ground having 600 mm depth was prepared with 40 and 60% relative density. Prefabricated vertical drains were then installed at triangular pattern having c/c spacing of 200 mm. Then the ground was subjected to repeated incremental acceleration loading of 0.1, 0.2, 0.3, and 0.4 g with 5 Hz frequency. In repeated shaking events, subsequent acceleration loading was applied only after complete dissipation of generated pore water pressure from previous loading. The effect of pore pressure response, liquefaction resistance, and improvement in soil density with and without prefabricated vertical drains was continuously monitored and estimated. The efficiency of PVD improved ground subjected to repeated acceleration loading was assessed and the results were presented.