台阶边坡非饱和渗流随机场及参数敏感性分析

Parameter sensitivity and unsaturated stochastic seepage field of bench slope

为了研究岩体渗透系数的空间变异性对露天矿边坡安全稳定性的影响,基于非饱和渗流理论和随机场理论建立了多台阶边坡渗流随机场模型。根据渗透系数与基质吸力的经验公式和非饱和岩体抗剪强度修正公式,利用Fish语言修正非饱和渗流区渗透系数、抗剪参数等力学参数,借助MATLAB实现渗透系数随机场和Monte-Carlo抽样的非侵入式随机算法,研究渗透系数的变异系数及水平、竖直相关距离对台阶边坡的安全系数及可靠度影响规律,分析台阶边坡可靠度指标对渗透系数变异性的敏感程度。结果表明,非侵入式随机方法实现随机场简单且易于实现,采用渗流随机场进行渗透系数赋值使模型更接近实际边坡状态,可以很好地反映渗透系数的空间变异性。考虑渗透系数空间变异性时的台阶边坡安全系数均值比渗透系数为定常数时小,即客观反映了对边坡安全稳定的保守估计。台阶边坡可靠性指标与渗透系数的变异系数呈线性负相关,与渗透系数的水平及竖向相关距离正相关。边坡安全系数及可靠度指标对渗透系数的变异系数更敏感。研究结论可为开展考虑渗流随机场边坡的变形破坏仿真分析提供参考。

The spatial variability of the mechanical properties of rock mass exists objectively,thus it is necessary to study its influence on the stability of slopes.This paper intends to present a stochastic seepage field model based on the saturate-unsaturated seepage theory and the stochastic field theory.Based on the empirical formula of the saturated hydraulic conductivity and the matrix suction and the shear strength modified formula of the unsaturated rock mass,the FISH language was used to modify the mechanical parameters of the rock mass,the saturated hydraulic conductivity(k),the shear strength parameters(c,φ),etc.Routines for the improvement of the capability of unsaturated seepage calculation of FLAC;software were programmed.A non-intrusive stochastic method was realized via MATLAB.The purpose of this paper is to obtain the reliability and the safety factor change rules of a bench slope and the parameter sensitivity,the coefficient of variability of k,the vertical and the horizontal correlation distance were analyzed.The results of the above research show that a stochastic field is easy to obtain using the non-intrusive stochastic method.The seepage stochastic field can reflect the spatial variability k,which is closer to actual.Therefore,ignoring the spatial variability of k may lead to unconservative estimates of failure probability.The safety factor of the bench slope,which is obtained by considering the spatial variability of k,is smaller than that obtained ignoring the spatial variability.The reliability index of the bench slope has a negative linear correlation with the variation coefficient k while has a positive correlation with the vertical or horizontal correlation distance of k.The slope safety factor and the reliability index are sensitive to the variation coefficient of k.The present study provides a useful reference for the simulation analysis of the deformation and failure of bench slopes and the prevention and reduction of disasters.