金川水电站地下洞室围岩初始地应力分布规律研究

Study on the Initial Geostress Distribution Law of Surrounding Rock of Underground Cavern of Jinchuan Hydropower Station

大型地下洞室群岩体初始地应力分布规律对洞室开挖过程中的围岩稳定有着重要影响。采用水压致裂法对岩体初始地应力进行量测;在有限元软件Miads中,以实际地形建立大范围的有限元模型,对地下洞室群附近岩体的初始地应力场进行反演分析。结果表明,地应力大小分布与地表地势高低具有一定关系,距离岸边一定范围内,靠近河谷方向主应力由增大转为减小;地下洞室围岩最大主应力值为5.81~8.31 MPa,最大水平主应力方向集中在N65°E~N80°E,量值为4.0~6.0 MPa,水平侧压力系数为0.69~1.28。地下洞室围岩应力场由自重应力和构造应力叠加而成,属于低应力地区。

The distribution law of initial geostress of rock mass in large underground cavern group has an important influence on the stability of surrounding rock during the excavation process of caverns.The initial geostress of the rock mass is measured by the hydraulic fracturing method,and a large-scale finite element model based on the actual terrain is established through the finite element software Miads,and the inversion analysis on the initial geostress field of the rock mass near the underground cavern group is carried out.The results show that the distribution of geostress is related to the surface topography.Within a certain range from the shore,the principal stress in the direction of the river valley changes from increasing to decreasing;the maximum principal stress value of the surrounding rock of underground caverns is 5.81~8.31 MPa;the direction of the maximum horizontal principal stress is concentrated in N65°E~N80°E with the magnitude of 4.0~6.0 MPa,and the horizontal side pressure coefficient of 0.69~1.28.The stress field of the surrounding rock of the underground cavern is formed by the superposition of self-weight stress and tectonic stress,which belongs to the low stress zone.