Mitigating liquefaction-induced displacements of shallow foundation using helical piles

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 lessen liquefaction-related damages while minimising cost and environmental impacts. This study aims to evaluate the use of helical piles as a possible technique to mitigate the settlement, tilting, and sliding of shallow foundations during seismic liquefaction. For this purpose, 12 1g shaking table tests were conducted on loose saturated sand under harmonic base input for (a) free-field condition, (b) a model foundation on the soil surface and (c) a model foundation underpinned by helical piles. The effects of input amplitudes and the number of helical piles were investigated in terms of acceleration response, excess pore-water pressure 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.