开挖尺寸效应对基坑稳定性的影响分析

Analysis on the Influence of Excavation Size Effects on Foundation Pit Stability

国内规范最主要的基坑抗隆起稳定性计算方法为圆弧滑动法,其假定滑动圆弧的圆心位于最下道支撑与围护墙的交点,但未考虑基坑开挖的尺寸效应,导致窄基坑设计偏于保守。为综合分析各种基坑抗隆起稳定性计算方法的差异性,研制基坑稳定性分析软件,并利用有限元强度折减法对各种计算方法进行对比分析。结果表明:基坑开挖尺寸对基坑抗隆起具有一定影响,相同条件下,开挖尺寸越小,其抗隆起安全系数越大,影响也更为显著,规范设计就越偏于保守;当增大开挖尺寸时,其对抗隆起安全系数的影响逐渐减小。

Slip circle method is the main method to calculate heave-resistant stability of foundation pit in Chinese standard.This method assumes that the center of slip arc is located at the intersection of the lowest support and retaining wall,which does not consider the size effects of foundation excavation,leading to the conservative design of narrow foundation pit.A foundation pit stability analysis software is developed in this paper for comprehensively analyzing the difference of various calculation methods of foundation pit heave-resistant stability,which apply the finite element strength reduction method to compare and analyze different calculation methods.The results indicate that the excavation size of foundation has a certain influence on the heave-resistant of foundation pit.Under same conditions,heave-resistant safety factor is increased with excavation size decreased,while the influence is becoming more significant.At this moment,the design based on standard is becoming more conservative.On the contrary,the influence on heave-resistant safety factor is decreasing with the excavation size increased.