基于点估计—有限元法的地下厂房开挖变形与扰动的概率分析

Probability Analysis of Deformation and Disturbance of Underground Powerhouse Excavation Based on PEM-FEM Method

大型地下厂房沿轴线方向一般可达几百米,导致岩体材料参数存在一定的空间变异性,采用确定性参数取值必然导致分析结果与工程实际之间存在差异,影响厂房的围岩扰动和稳定性判断。对此,将点估计—有限元的概率分析方法应用到地下厂房围岩变形的概率分析中,研究岩体力学参数空间变异的概率处理方法对围岩稳定性的影响;通过分析围岩变形及扰动,提出了一种基于变形标准差的围岩开挖扰动敏感性判断方法。以某抽水蓄能电站为例,采用正态分布描述了围岩力学参数的空间变异性,进而设计了16种地下洞室群围岩开挖稳定性分析方案。结果表明,采用考虑岩体力学参数空间变异性的概率分析方法能够准确判断出围岩各部位可能的变形量值,为稳定性判断提供更准确的依据;基于提出的开挖扰动敏感性判断方法能直接描述围岩开挖形成的关键扰动区域,在研究案例的地应力和节理分布等地质条件下,开挖扰动敏感区域主要为高边墙处。

Large underground powerhouse can generally reach several hundred meters along the axis directions,resulting in certain spatial variability of material parameters of the rock masses.The use of deterministic parameters of the rock masses will inevitably lead to differences between the numerical results and the practice,affecting the analysis of the disturbance and stability of the powerhouse.To solve this problem,the point estimate method and finite element method(PEM-FEM)is used to the probabilistic analysis of the deformation of underground powerhouse,and the impact of the PEM/FEM considering the spatial variation of mechanical parameters of the rock masses on the stability of powerhouse is studied.Through the analysis of the deformation and the excavation disturbance,a method for judging the sensitivity of the excavation disturbance was proposed based on deformation standard deviation.In the case study of a pumped storage power station,normal distribution was used to describe the spatial variability of mechanical parameters of the rock mass,and 16 kinds of parameter combination schemes were designed for simulating the excavation of the caverns.The results show that the method considering the spatial variability of mechanical parameters can accurately determine the deformation,which can provide more accurate guidance for stability analysis;The proposed sensitivity analysis method for excavation disturbance can directly describe the key disturbance zone formed by the excavation,for example,under the geological conditions such as in-situ stress and joint distribution of the research case,the excavation disturbance sensitive area is mainly the high side wall.