基于上限分析的空间变异土质边坡可靠度

Reliability of spatially variable earth slopes based on the upper bound analysis

空间变异性是土体的固有不确定性。采用随机场理论表示土体的空间变异性,通过Karhunen–Loève(KL)展开法进行随机场的离散。使用基于离散机构的边坡上限分析,在生成速度间断面时考虑空间各点的内摩擦角随机场离散结果,并联合使用强度折减法、二分法及序列二次规划法求解边坡的安全系数,采用一阶可靠度方法(FORM)和子集模拟(SS)进行边坡的可靠度分析。针对SS与强度折减法的特点,提出二者耦合的优化算法以提高计算效率。通过对某土质边坡的计算分析,阐明了基于KL展开法的FORM及SS在求解边坡可靠指标及失效后果的异同点,分析了土体强度参数变异系数对边坡可靠指标与失效后果的影响规律,为进行边坡的风险分析与防治提供了理论依据。

The spatial variability is an inherent uncertainty of soils.The random field theory is used to represent the spatial variability of soils,and the random field discretization is performed by the Karhunen-Loève(KL) expansion method.Using the slope upper bound analysis based on the discrete mechanism,the discretization results of the internal friction angle random field at each point in the space are considered when generating the velocity discontinuity surface.The upper bound analysis,shear strength reduction technique,bisection searching,and sequential quadratic programming method are combined to solve the safety factor of slopes.The first-order reliability method(FORM) and subset simulation(SS) are employed for slope reliability analysis.Given the characteristics of SS and the shear strength reduction technique,an optimization algorithm coupling the two is proposed to improve computational efficiency.By calculating and analyzing an earth slope,the similarities and differences between FORM and SS based on the KL expansion method in solving the slope reliability index and failure consequence are clarified.The influence of the variation coefficient of soil strength parameters on the slope reliability index and failure consequence is investigated,providing a theoretical basis for risk analysis and prevention of slopes.