排水刚性桩单桩抗液化性能的振动台试验研究

排水刚性桩是一种将竖向排水体与刚性桩相结合的新型桩基。为研究抗液化排水刚性桩的单桩抗液化作用效果,采用振动台试验对排水刚性桩在动力荷载作用下的排水效果、地基孔压响应、加速度响应以及在上覆荷载作用下桩顶的侧向永久位移等动力响应进行了研究,并与不设排水体的普通桩作了对比。结果表明:抗液化排水刚性桩是一种有效的抗液化措施。在排水刚性桩桩身1倍桩径范围内,土体的喷砂冒水现象得到有效控制,普通桩试样中喷砂冒水现象严重。距离桩身排水通道0.5倍桩径处,排水桩超孔压比峰值约为普通桩超孔压比峰值的50%,排水桩可以更快地消散地基内的超孔压,超孔压比从峰值减小为0.7时,排水刚性桩用时6 s,普通桩用时17 s。排水刚性桩距排水体0.5倍桩径处加速度峰值为0.2g,相同测点处普通桩加速度峰值为0.09g,与排水桩相比,减少约100%。随加载过程的持续,排水桩桩顶震荡幅值基本不表现,在惯性力作用下,振动荷载初始时间段内(3 s时间内),桩身发生轻微震荡。普通桩桩顶水平震荡幅值为0.6 cm,且震荡时间持续整个加载过程中(10 s),普通桩桩顶的侧向永久位移约为排水桩的3倍。

Shaking table tests on liquefaction resistance performance of single rigid-drainage pile

The rigid-drainage pile is a new type of pile which combines vertical drainage and rigid pile. To investigate the liquefaction resistance, the drainage, response of excess pore water pressure, acceleration and lateral permanent displacement of pile head under upper loads are measured based on shaking table tests. The results are compared with those of ordinary pile tests. It is indicated that the rigid-drainage pile is an effective approach for mitigation of liquefaction. The phenomenon of sand boil is restrained effectively in the range of one time the pile diameter, while sand boil occurs significantly in ordinary pile tests. The peak of excess pore water pressure ratio of rigid-drainage pile tests is 50% of that of ordinary pile ones at a distance of 0.5 time the pile diameter, and the rigid-drainage pile can dissipate the excess pore water pressure more rapidly. It takes 6 s for the peak of excess pore water pressure ratios to decrease to 0.7 in the rigid-drainage pile tests, and in the ordinary pile tests it is 17 s. The peak of acceleration is 0.2g at a distance of 0.5 time the pile diameter, and it is only 0.09g in the ordinary pile tests at the same monitor point, which means that the peak of acceleration in ordinary pile tests is decreased by 100% approximately compared to that of rigid-drainage pile. With the continuation of loading process, the amplitude vibration of rigid-drainage pile head is tiny, and it only occurs in the initial moments (3 s). The peak lateral permanent displacement is 0.6 cm in the ordinary pile tests and the amplitude vibration continues to the end of shaking. The peak lateral permanent displacement is around