基于可靠性的复合土钉支护基坑稳定性分析

Reliability-based stability analysis of a foundation pit supported by composite soil nailing

针对预应力锚杆复合土钉支护基坑内部整体稳定的可靠性计算问题,以边坡极限平衡理论与圆弧滑动面法为基础,应用扰动力法建立了基坑内部整体稳定性分析的功能函数与最危险滑动面的计算模型.通过SLP优化法与单形调优法实现了最危险滑动面的优化搜索.以土体的抗剪强度指标作为随机变量,应用AFOSM(2)法计算了基坑内部整体稳定可靠性指标,并结合工程实例进行了分析.分析表明:基坑内部整体稳定的可靠性指标β受土体粘聚力、内摩擦角与摩阻力变异系数的影响较大,且随变异系数的增大而减小;其中,内摩擦角的变异系数对β的影响最大,摩阻力的变异系数对β的影响最小;并且在基坑开挖深度范围内,中下部土层对β的影响较大,上部土层对β的影响较小.

In order to establish the reliability calculation of the inner global stability of a foundation pit supported by a prestressed anchor composite soil nailing, and based on the slope limit equilibrium theory and the circular sliding surface method, the state equation of limit equilibrium and the calculation model of the most dangerous sliding surface for inner global stability of a foundation pit was established using the disturbing force method. Additionally, the searching and solving method of the most dangerous sliding surface was optimized with the sequential linear programming （SLP） optimization method and the simplex optimization method. Then with the shear strength indexes of soil as random variables, the reliability index of inner global stability of the foundation pit was calculated using the advanced first order second moment method （AFOSM） （2） method, and a practical project was used for final analysis. The analysis shows that the reliability index of the inner global stability of the foundation pit is affected greatly by the coefficients of the variability of the cohesion, internal friction angle, and friction of soil, and also decreases with the increase of the coefficient of variability. The reliability index is affected the most by the coefficient of the variability of the internal friction angle and the least by the coefficient of the variability of the friction. Within the depth of the excavation, the reliability index is affected more by the middle and lower soil layers and less by the up per soil layers.