基于裂隙网络有限元的地下洞室围岩位移反演分析

Back Analysis of Surrounding Rock Displacement of Underground Cavern Based on Fracture Network Finite Element Method

以某水电站地下洞室围岩局部失稳现象为研究案例,考虑围岩裂隙结构面的随机性和统计分布特征建立二维裂隙网络有限元模型,通过裂隙参数的抽样检查以及进行洞室开挖模拟试算,验证了生成裂隙网络与实际岩体结构的一致性以及裂隙结构面相关力学参数取值的合理性。进一步采用正交设计与神经网络算法形成基于裂隙网络有限元的位移反演分析方法,基于反演力学参数的正向计算结果与施工期地质调查及围岩稳定评价基本相符,可以反映裂隙围岩主要变形特征与失稳机制,并为裂隙结构面力学参数的获取提供了新的研究思路。

Based on the geological data revealed during the excavation of the underground cavern of Dagangshan Hydropower Station,a twodimensional finite element model of fracture network is established.Considering the randomness and statistical distribution characteristics of the deformation of the fracture surrounding rock,a displacement inversion analysis method based on the fracture network finite element is formed.The forward calculation results based on the inversion mechanical parameters are basically consistent with the geological survey and the surrounding rock stability evaluation during the construction period,which can reflect the main deformation characteristics and instability mechanism of the fractured surrounding rock.It shows that the fracture network model established in this paper and the correlation inversion analysis method have good adaptability in engineering.It is found that the shear and opening deformation mainly occur in the process of excavation and unloading of the fracture structure surface,among which the stress relaxation of the gently inclined structure surface has a great influence on the surrounding rock,and the stress relaxation area is basically the same as the area where the surrounding rock loosens,which shows that the shear opening deformation of the fracture surrounding rock during the excavation and unloading process is the main reason for the stress relaxation of the surrounding rock.