基于系统可靠度方法的板式支护体系基坑抗隆起研究

Analysis of Basal Heave Failure Stability of Embedded Wall Based on System Reliability

板式支护体系下的基坑因具备足够的刚度和强度可能发生圆弧滑动而出现隆起破坏,坑底地基失稳也可能引起地基极限承载力剧降。考虑到参数的变异性,常规的方法得到的基坑抗隆起稳定性系数可能并不安全,为此提出将板式支护体系下基坑的隆起破坏视为两种破坏模式组成的串联系统,利用常用的可靠度分析方法验算点法(FOSM)分别求出单个破坏模式的可靠度指标,结合逐步等效平面法求出系统的可靠度指标,进而求出系统失效概率,并通过算例对基坑的抗隆起稳定性进行评价。结果表明,基坑的抗隆起破坏可能受任一种破坏模式的控制,因此采用系统可靠度方法评价基坑的抗隆起稳定性更接近工程实际。

With sufficient stiffness and strength of the embedded wall,bulge fracture may occur because of circular sliding or foundation failure.Taking the variability of the parameters into consideration,coefficient of bulge fracture＇s stability of the foundation pit obtained by the traditional method may not safe.For this purpose,we regard the bulge fracture of embedded wall as one series system composed by two damage forms.The reliability index of a single failure mode is calculated by first order reliability method（FORM）,which is the common method of reliability analysis.Combined with step-by-step equivalent plane method,we get the failure possibility of the system.The stability of foundation pit is evaluated though cases.The results show that bulge fracture of foundation pit may be controlled by any kind of damage form.So,it is more close to the engineering practice when we use system reliability method to evaluate the bulge fracture stability of foundation pit.