RESEARCH ON ELEMENT FAILURE PROBABILITY AND FAILURE MODE OF SOIL SLOPE
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摘要:
土质边坡系统失效概率与土体抗剪强度参数以及地下水位息息相关,在传统边坡可靠度分析中一般只考虑了土体抗剪强度参数的变异性,忽略了地下水位随机性带来的影响。该文将有限元离散技术、上限法理论、相关非高斯随机场模拟方法以及随机规划理论结合起来研究随机地下水位作用下考虑参数空间变异性的边坡系统失效概率。采用有限单元离散边坡土体,将边坡地下水位作为随机变量并考虑土体抗剪参数的空间变异性,基于塑性极限分析上限法构建边坡可靠度分析的随机规划模型;采用基于蒙特卡洛的迭代方法进行求解,得到边坡稳定性系数和速度场;根据边坡中单元的失效信息首次采用AP聚类分析方法来估算边坡的系统失效概率,发展了边坡系统可靠度分析理论。对一个经典的边坡算例进行了系统分析并与极限平衡分析方法、有限元方法结果进行对比,结果表明:随机地下水位作用下考虑参数空间变异性时,边坡存在多种失效模式,AP聚类分析方法可以根据失效单元的位置信息识别出边坡所有失效模式以及对应的失效概率;基于Matlab编制了高效的上限法并行程序,大大提高了计算效率。
Abstract:The failure probability of a soil slope system is strongly related to soil shear strength parameters and groundwater level. In the traditional slope reliability analysis, only the variability of soil shear strength parameters is generally considered, and the influence of random groundwater level is ignored. Finite element discrete technique, upper bound method theory, relevant non-Gaussian random field simulation method and, stochastic planning theory are combined to study the failure probability of the slope system under the effect of stochastic groundwater level considering the spatial variability of parameters. A stochastic programming model for slope reliability analysis is constructed upon the upper bound method for plastic limit analysis by using a finite element discrete slope soil body, taking the groundwater level of the slope as a random variable and considering the spatial variability of the soil shear parameters, and then the model is employed to obtain the stability safety coefficient and velocity field of the slope upon Monte Carlo simulation; the AP clustering analysis method is used for the first time to the system failure probability of the slope estimated based on the failure information of the elements in the slope, and the reliability analysis theory of the slope system is developed. A classical slope calculation case is systematically analyzed and compared with the results of Limit Equilibrium Analysis Method and Finite Element Method. The results show that: there are multiple failure modes of slopes under the action of random groundwater level considering the spatial variability of parameters, and the AP cluster analysis method can identify all the failure modes of slopes and the corresponding failure probabilities based on the location information of failed elements; an efficient parallel program of upper bound method is prepared upon Matlab, which greatly improved computing efficiency.
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Keywords:
- slope /
- reliability /
- spatial variability /
- random groundwater level /
- upper bound method
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表 1 土体参数统计特性
Table 1 Statistics of soil parameters
土体参数 均值 变异系数 分布类型 波动范围 相关系数 黏聚力c/kPa 10 0.3 对数正态 Lh=40 m ρc,φ=−0.5 摩擦角φ/(°) 30 0.2 对数正态 Lv=4 m 表 2 不同方法的边坡可靠度结果对比
Table 2 Comparison of slope reliability results of different methods
表 3 三种水位作用下边坡的可靠度指标
Table 3 Calculation results of reliability index
水位 计算方法 均值uk 标准差σk 失效概率PZf/(%) tw=1 UBM 1.201 0.096 1.10×10−2 LEM 1.199 0.106 1.71×10−2 FEM 1.226 0.097 0.60×10−2 tw=25 UBM 1.143 0.090 4.50×10−2 LEM 1.143 0.097 5.60×10−2 FEM 1.168 0.090 2.40×10−2 tw=50 UBM 0.894 0.070 92.70×10−2 LEM 0.892 0.069 93.40×10−2 FEM 0.916 0.071 89.40×10−2 表 4 边坡失效模式以及对应的失效概率
Table 4 Slope failure mode and the corresponding failure probability
失效模式 失效面积/m2 失效次数 失效概率PZf/(%) 模式1 5.45~7.41 526 1.052 模式2 10.35~15.52 667 1.334 模式3 48.72~53.44 3342 6.684 模式4 69.43~72.42 1088 2.176 模式5 89.45~92.91 122 0.244 模式6 110.05~112.65 64 0.128 总和 − 5809 11.618 表 5 不同地下水位作用下边坡失效模式以及对应的失效概率
Table 5 Slope failure modes and corresponding failure probabilities under the action of different groundwater levels
地下水位 失效模式 失效次数 失效概率PZf/(%) tw=1 模式3 8 0.800 tw=25 模式3 13 1.300 模式4 12 1.200 tw=50 模式1 219 2.190 模式2 178 1.780 模式3 340 3.400 模式4 155 1.550 模式5 26 0.260 模式6 9 0.090 -
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