Mitigating Liquefaction-Induced Displacements of Shallow Foundation using Helical Piles

Abstract

During previous earthquakes, displacements of shallow foundations on liquefiable sites caused significant damage to overlying super-structures leading to casualties and catastrophic economic loss. Various countermeasures have been developed to minimize liquefaction-related damages while minimizing cost and environmental impact. This study aims to evaluate the use of helical piles as a possible technique to mitigate the settlement, tilting, and sliding of shallow foundations on the liquefiable ground in seismic conditions. For this purpose, twelve 1g shaking table tests were conducted on uniform loose saturated Babolsar sand subjected to harmonic base input motion for (1) free-field condition, (2) a model foundation on the soil surface, and (3) a model foundation underpinned by helical piles. The effects of input motion amplitudes and the number of helical piles were investigated in terms of acceleration response, excess pore water pressure (EPWP), and foundation displacements. The results confirmed the satisfactory performance of helical piles in reducing shallow foundation displacements. In particular, the mean permanent settlements were reduced by 45% and 75% when using four and eight helical piles, respectively. Similar trends were observed for the shallow foundation permanent tilting and sliding; permanent tilting was reduced by 30% and 59% when using four and eight helical piles, respectively, while these results were 45% and 68% for the sliding.