大岗山水电站地下厂房区三维地应力场反演分析

Three dimensional back analysis of geostress field in underground powerhouse zone of Dagangshan hydropower station

初始地应力场是地下厂房工程设计和稳定性分析的重要依据,通常工程区实测地应力点较少,必须在有限的地应力资料基础上,采用反演分析方法获得整个工程区地应力场。结合大岗山水电站地形地貌条件和地质结构特征,基于地下厂房区地应力实测资料,研究了地下厂房区地应力场分布特征;在此基础上,采用有限元数学模型多元回归方法,进行了大岗山水电站地下厂房地应力场三维反演分析研究,获得了地下厂房区域地应力分布规律和影响因素的认识。结果表明,大岗山工程区地应力场分布受构造应力、地质构造和地形地貌的综合影响,岩性对地应力影响较小,岩脉与断层影响显著;在地下厂房区最大水平主应力σH、最小水平主应力σV、铅直向应力σh关系为σH>σV>σh,地应力量值中等,侧压力系数垂直厂房轴线方向为0.5～0.6,轴线方向为1.1～1.3。

Initial geostress field is very important for engineering design and stability analysis of underground engineering.The back analysis method is often adopted to get the whole geostress field of engineering zone based on the limited measured data.Based on the measured geostress data,geographic and geomorphic conditions and characteristics of geologic framework,the distributing characters of geostress field in underground powerhouse zone of Dagangshan hydropower station are studied.Furthermore,the multiple regression method is applied to back analyze the three dimensional geostress field of underground caverns of Dagangshan hydropower station;and the distributing rule and influence factor of geostress are also discussed.The results show that： the geostress field in underground powerhouse zone of Dagangshan hydropower station is affected by tectonic stress,geologic structure,terrain and physiognomy;among them,lithology has little influence;dyke and fault have great influence;the value of geostress is medium and there is,where is maximum horizontal principal stress;is minimum horizontal principal stress;is vertical stress;the lateral pressure coefficient vertical to powerhouse axis is 0.5～0.6,along powerhouse axis is 1.1～1.3.