基于Plaxis 2D的“吊脚桩”刚度对支护的影响分析

Effect of the stiffness of 'End-Suspended Pile' for the foundation pit supporting based on Plaxis 2D

在青岛地区,上层是土体、下层是岩体的岩土二元结构基坑非常普遍.在这种复合地层地质条件下采用通常的桩锚(撑)体系时,在坚硬岩层中施工灌注桩难度大、工效差、桩的入岩深度不够,难以形成理想的桩锚(撑)支护体系,导致支护桩处于无嵌固状态,出现所谓的"吊脚桩",对此国内外尚无成熟的计算模式.借助Plaxis 2D有限元分析程序,模拟采用"吊脚桩"支护基坑的开挖过程并与实际监测数据进行对比,再通过将不同刚度的支护桩的变形进行对比来找到最合理的支护刚度,用以指导工程实际.

Foundation pits with dualistic structure of soil stratum and underlying rock stratum are commonly through Qingdao area. When the usual pile-anchor-insert systems are used in Qingdao area ＂rock under soil＂ compound formation geologic conditions,it is a difficult and poor efficiency to construct piles in hard rock. The pile into rock depth is not good enough and it is difficult to form ideal pile-anchor-insert systems. The supporting pile without build- in state will appear the so-called ＂End-Suspended Pile＂ which has no mature calculation mod- el at home and abroad. With finite element analysis program of Plaxis 2D, foundation pit ex- cavation has been simulated and compared with actual monitoring data in this article. Through a comparison of the different deformations of the stiffness of retaining pile, this article tries to find out the most reasonable supporting stiffness to guide the engineering practice.