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.

中文翻译：

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使用螺旋桩减轻浅基础液化引起的位移

在以往的地震中，可液化场地上的浅地基位移对上覆的上部结构造成了严重破坏，导致人员伤亡和灾难性的经济损失。人们已经制定了各种对策来减少液化相关的损害，同时最大限度地减少成本和环境影响。本研究旨在评估使用螺旋桩作为减轻地震液化过程中浅基础沉降、倾斜和滑动的可能技术。为此，在谐波基础输入下对松散饱和砂进行了12 次 1 g振动台试验，测试条件为 ( a ) 自由场条件、( b ) 土壤表面的模型基础和 ( c)）由螺旋桩支撑的模型基础。从加速度响应、超孔隙水压力和地基位移方面研究了输入振幅和螺旋桩数量的影响。结果证实了螺旋桩在减少浅基础位移方面具有令人满意的性能。特别是，使用四个和八个螺旋桩时，平均永久沉降分别减少了 45% 和 75%。浅基础永久倾斜和滑动也观察到类似的趋势：使用四个和八个螺旋桩时，永久倾斜分别减少了 30% 和 59%，而滑动的结果分别减少了 45% 和 68%。