考虑力学参数不确定性的岩质边坡开挖卸荷响应概率评价

Probabilistic evaluation of excavation unloading response of rock slope considering the uncertainty of mechanical parameters

鉴于目前关于节理岩体力学参数空间变异性表征及存在潜在滑移面边坡的可靠性问题研究较多,但对于岩质边坡力学参数空间变异性影响及开挖卸荷响应(变形与塑性区)不确定性分析的研究较为有限。提出考虑力学参数不确定性的岩质边坡开挖卸荷响应概率评价方法,该方法以室内岩石力学试验及现场地质勘察测绘数据为基础,利用Hoek-Brown经验准则与Monte Carlo分析手段,构建了以岩石单轴抗压强度(uniaxial compressive strength,简称UCS)、地质强度指标(geological strengthindex,简称GSI)和节理工程参数为输入的边坡岩体力学参数概率统计模型,并采用卡方检验进行模型的吻合度检验;基于点估计原理构建岩体力学参数组合方案,并结合数值模拟开展边坡开挖过程的仿真分析,获得边坡开挖后整体安全系数及位移及塑性区的概率分布。利用该方法对在建京秦高速沿线某路堑边坡岩体力学参数及开挖卸荷响应进行分析,得到了岩体强度、弹性模量、黏聚力与内摩擦角的取值及不确定性分布,采用点估计与FLAC3D模拟分析,得到了边坡安全系数及典型观测点的位移与塑性区分布结果,并与实测值进行对比,结果表明该方法的适用性较高。该研究为岩质挖方边坡的力学参数估计及稳定性分析评价提供了一种有效途径,能够为实际工程施工决策提供重要参考依据。

There are many studies on the spatial variability of mechanical parameters of jointed rock masses and the reliability of slopes with potential slip surface,but the research on the spatial variability of mechanical parameters of rock slopes and the uncertainty analysis of excavation unloading response(deformation and plastic zone)is limited.A probabilistic evaluation method for excavation unloading response of rock slopes considering the uncertainty of mechanical parameters is proposed.Based on laboratory rock mechanical tests and geological survey mapping data,the probabilistic statistical models of rock mass mechanical parameters of slopes are constructed by using Hoek-Brown empirical criterion and Monte Carlo analysis method,in which the uniaxial compressive strength(UCS)of rocks,the geological strength index(GSI)and the parameters of rock mass joints are input,and these probabilistic models are checked by the chi-square test.Based on the point estimation principle,the combination scheme of rock mass mechanical parameters is constructed,and the simulation analysis of slope excavation process is carried out by the numerical method to obtain the probability distributions of the slope safety factor as well as the displacement and plastic zone of rock masses after excavation.This method is used to analyze the rock mass mechanical parameters and excavation unloading response of a cutting slope along the Beijing-Qinhuangdao expressway under construction.The values and uncertainty distributions of rock strength,elastic modulus,cohesion and internal friction angle are obtained.By using the point estimation and FLAC3D simulation method,the distributions of the slope safety factor as well as the displacement and plastic zone distributions of typical observation points are obtained.The comparison between the simulation results and the measured values shows the applicability of the proposed method.This study provides an effective way for the mechanical parameter estimation and stability evaluation of the rock cutting slope,and can provide a valuable reference for the decision-making process in practical engineering construction.