龙滩水电站左岸地下厂房区三维地应力场反演分析

BACK ANALYSIS OF 3D IN-SITU STRESS FIELD OF UNDERGROUND POWERHOUSE AREA OF LONGTAN HYDROPOWER STATION

在龙滩地下厂房区工程地质和试验洞变形监测结果综合分析的基础上,建立地质概化和试验洞施工开挖模型;采用地应力场随埋深变化呈线性分布的假设,并根据地应力测试成果,确定地应力场的分布区间。在此基础上,采用均匀设计方法和三维显式有限差分法,通过模拟试验洞的开挖变形,对龙滩水电站厂房区岩体地应力场进行了三维变形反演分析。对比计算位移和监测位移,计算各方案的位移目标函数,获得了岩体地应力场沿深度的分布规律。比较监测与计算位移,两者在量值上相当,在变形趋势上也基本相同,而且实测与计算所得的地应力值较吻合,表明所获得的岩体地应力场是基本合理的,同时说明此反演方法简便、有效。

Based on the comprehensive analysis of geological conditions and deformation monitoring, the simplified geological model and excavation model of the experimental cavity are set up. The assumption of linear distribution of in-situ stresses of rock masses along depth is adopted, and based on the in-situ stress measurement, the interval of in-situ stresses is decided for back analysis. Then, the uniform design method and FLAC3D are used to make back-analysis on in-situ stress field of the underground powerhouse area of Longtan Hydropower Station through simulating the excavation of the experimental cavity by steps. 12 excavation cases are selected for simulation. The displacement object function values are calculated for each case by steps. The minimization of object function is made, and the distribution regularity of in-situ stresses of rock masses along depth is obtained. By comparison of measured and calculated displacements and in-situ stresses of rock masses, it is shown that the obtained results are satisfactory and the presented back analysis is reasonable and effective.