考虑土体空间变异性的基坑可靠性分析

Reliability Analysis of Foundation Pit Considering Spatial Variability of Soil Mass

以南京江北服贸大厦基坑工程为研究对象,在考虑土体空间变异性的基础上,利用随机有限差分方法研究了土体剪切模量随机场对基坑变形的影响,以及土体粘聚力和内摩擦角随机场对基坑稳定性的影响.计算结果表明:基坑开挖区域卸载后,由于围护结构的支挡作用,支护桩发生侧移并且在基坑开挖面附近出现水平位移最大值;立柱随着开挖过程的进行产生隆起变形,最终趋于稳定.土体剪切模量空间变异性对基坑周围土体的位移影响较大,对持力层仍采用均匀性假设的支护结构的变形影响较小.最大深层水平位移和支护桩最大水平位移分别有81%和87%的概率超过确定性计算结果.在基坑稳定性分析中,以确定性计算结果为标准的基坑失效概率为25%,说明考虑土体空间变异性对基坑变形及其可靠性进行分析是很有必要的.

Based on the foundation pit project of Nanjing Jiangbei Service Trade Building,and considering the spatial variability of soil mass,the influence of the random field of soil shear modulus on the deformation of foundation pit and the influence of the random field of soil cohesion and internal friction angle on the stability of foundation pit are studied by using the stochastic finite difference method.The calculation results show that after the unloading of the excavation area of the foundation pit,due to the retaining effect of the retaining structure,the retaining pile moves laterally and the maximum horizontal displacement occurs near the excavation surface of the foundation pit;The column will bulge and deform within the excavation process,and finally tends to be stable.The spatial variability of soil shear modulus has a greater impact on the displacement of soil around the foundation pit,while a smaller impact on the deformation of the retaining structure with the assumption of homogeneity of the bearing layer.There are 81%and 87%probabilities of the maximum deep horizontal displacement and the maximum horizontal displacement of the retaining pile exceeding the deterministic calculation results respectively.In the stability analysis of foundation pit,the failure probability of foundation pit based on the deterministic calculation results is 25%,which shows that it is necessary to consider the spatial variability of soil in the reliability analysis of foundation pit deformation and stability.