嵌岩灌注桩抗拔承载特性现场试验研究

摘要

According to the vertical uplift static test data of single rock-socketed cast-in-situ pile in the new project of state grid 500 kV double-circuit line from Luping to Fule,the load transfer behavior of rock-socketed cast-in-situ piles and the characteristics of the frictional resistance in rock-socketed section are analyzed.The results show that the pile side ultimate resistance of strong weathered sandstone is 2.4 to 2.6 times of the value provided by Technical Specification for Building Pile Foundation and the pile side resistance of the moderately weathered sandstone is 635 ～ 770 kPa;the interaction between rock-socketed pile shaft and rock stratum should be the combination of friction force,cohesive force and the socketed force.When the test pile reaches the ultimate uplift load,the rock-socketed ratio of pit-depth to pit-diameter that the pile side resistance can effectively and completely play is 3.75.It is not correct that the larger the rock-socketed depth,the more effective to increase the uplift bearing force.%依据国家电网路平—富乐500千伏双回线路新建工程中嵌岩灌注桩单桩竖向抗拔静载试验数据,分析了嵌岩灌注桩荷载传递性状和嵌岩段摩阻力发挥程度.研究结果表明:静载试验测得的强风化砂岩层中桩侧极限阻力是《建筑桩基技术规范》推荐值的2.4 ～2.6倍,同时测得极限状态下中风化砂岩层中桩侧阻力为635 ～770 kPa;嵌岩段桩身与岩层的相互作用应是摩擦力、黏结力、嵌固力的综合作用;试桩在达到极限抗拔荷载时,桩侧阻力有效发挥的嵌岩深径比为3.75,并不是嵌岩深度越大对提高抗拔承载力越有效.