抗液化排水刚性桩沉桩过程中的孔压响应
Field tests on response of excess pore water pressures of liquefaction resistant rigid-drainage pile
-
摘要: 抗液化排水刚性桩是一种将刚性桩与竖向排水体相结合的新桩型,可用于提升饱和土地基在地震作用下的抗液化能力。基于某建筑桩基工程,首次开展了抗液化排水刚性桩和不含排水体的普通刚性桩的沉桩对比现场试验,分析了沉桩过程中桩周土体超孔隙水压力的增长及消散规律。试验结果表明:沉桩过程中,抗液化排水刚性桩对桩周超孔压的消散作用对于可液化土层所在的桩侧深部埋深处最明显(试验测点距桩心2倍桩径、埋深-15 m),该处排水桩的超孔压峰值为普通桩的1/4到1/2,排水桩消散70%峰值超孔压所需时间仅为普通桩的1/3;在深部埋深(-15 m),排水桩的最大影响半径为2~4倍桩径,在上中部埋深(-5 m、-10 m),排水桩的最大影响半径为4~8倍桩径;在影响范围内,同位置排水桩对深部可液化土层超孔压的消散作用要大于上中部埋深土层。现场试验数据为抗液化排水刚性桩的桩间距选择提供了有力的设计参考依据。Abstract: The liquefaction resistant rigid-drainage pile is a new type of pile which can be used in geotechnical earthquake engineering. The pile combines the bearing capacity of rigid pile and the drain-ability of gravel pile. Based on the pile foundation engineering of Jiangyin No.1 High School's new campus, the pile-driving field tests on liquefaction resistant rigid-drainage pile are carried out for the first time. The excess pore water pressures around drainage piles and ordinary piles are recorded during field tests, depending on various data from different locations in depths and displacements. According to these test results, the maximum excess pore water pressure around the ordinary piles is larger than that around the drainage piles during the pile driving. When the pile driving is finished, the excess pore water pressures around the drainage piles dissipate faster than those around the ordinary piles. In the influence area, the excess pore water pressure dissipation of drainage piles at deep depths where a liquefiable soil layer is located is more obviously than that at shallow depths. The data of piles tests may provide other engineers with reliable evidences.