排水刚性桩沉桩挤土效应的现场试验研究

Field tests on squeezing effects of the rigid-drainage pile

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。基于江阴一中新建教学楼桩基工程,开展了排水刚性桩与不含排水体的普通刚性桩的沉桩对比现场试验,实时动态监测排水桩与普通桩桩周土体中不同距离及深度处的水平位移、侧向土压力及孔隙水压力的变化情况,研究排水刚性桩的沉桩挤土效应。试验结果表明:排水桩能够减小沉桩过程中桩周土体因桩身挤土而发生的侧向水平位移,在距桩心3倍桩径处,排水桩桩周土体的最大水平位移为普通桩的1/6,在距桩心6倍桩径处,排水桩为普通桩的2/5;排水桩能够大幅降低桩周土体因沉桩挤土而产生的超孔隙水压力,深度15m,距离桩中心2倍桩径处,排水桩的超孔压峰值仅为普通桩的1/4;排水桩能够减少沉桩过程中桩周土体的挤土压力,降低沉桩挤土对桩周原有土压力的影响,在深度15m距桩心2倍桩径处,排水桩的土压力变化的峰值仅为普通桩的1/4。现场试验数据为排水刚性桩的工程应用提供了设计参考依据。

The rigid-drainage pile is a new type of pile which combines a rigid pile with vertical drainage components. Based on the pile foundation project in new campus of Jiangyin No. 1 High School, field tests on pile driving of the rigid- drainage pile and the ordinary rigid pile without drainage were carried out. The horizontal displacements, soil stresses and excess pore water pressures around drainage piles and ordinary piles were monitored and compared to study the squeezing effects of the rigid-drainage pile. The results show that the rigid-drainage pile can reduce the horizontal displacement of surrounding soil during the pile driving. At the position of 3 times the pile＇ s diameter from the pile center, the maximum horizontal displacement of soil for the rigid-drainage pile is 1/6 of that for the ordinary pile. At the distance of 6 times, the ratio is 2/5. The rigid-drainage pile can greatly reduce the excess pore water pressure and soil stresses caused by the pile driving. At the location of 2 times the pile＇ s diameter far from the pile center in the depth of 15m, the peak excess pore water pressure is only 1/4 of that of the ordinary pile, and the ratio of the peak earth pressure between two types of piles is 1/4. The field test data provide the design reference for practical applications of the rigid- drainage pile.