糯扎渡水电站^#2导流洞三维非线性有限元反分析

Back analysis for the diversion tunnel No.2 of Nuozhadu Hydropower Station by use of 3D nonlinear finite element method

糯扎渡水电站#2导流隧洞开挖经过F3断层,开挖过程中,F3断层影响带附近的岩体力学参数直接控制着围岩的变形和应力分布。为了评判后续Ⅱ、Ⅲ层开挖围岩的稳定性,需要反演出F3断层附近围岩的岩体力学参数和初始地应力场。对于隧洞开挖反分析问题,考虑到现场位移监测数据与隧洞开挖之间的相互关系,采用开挖位移增量形式进行反分析,并且分析了三维非线性有限元以开挖位移增量的均方误差作为目标函数的反分析计算过程。为了减少现场的位移量测数据对反分析结果的影响,改善其规律性,采用多元线性回归模型对位移监测数据进行整理,有效的提高了反分析计算结果的精度。最后,利用上述方法反演得到了#2导流隧洞F3断层附近岩层的岩体力学参数和初始地应力场。

Excavation of the diversion tunnel No. 2 of the Nuozhadu Hydropower Station passed through the faultage F3. During the process of excavation, the strain and stress distribution of adjoining rock were controlled by the mechanics parameters of rock mass around the influential cingulum of fanltage F3. IN order to evaluate the stability of adjoining rock because of the excavation of layers Ⅱ and Ⅲ, the back analysis of mechanical parameters and the initial stress filed of the rock around the faultage F3 was needed. According to the back analysis of the tunnel excavation, the relationships between the monitored data of displacement in situ and the excavation of the tunnel should be considered, so the displacement increment of excavation was used in the back analysis, and the computing process of 3D nonlinear finite element method in which the average error of excavation displacement increment was used as the target function was analyzed. To decrease the error of the back analysis influenced by the displacement data in situ, the monitored displacement data were dealt by the multi-linear recursive model, and the precision of results of the back analysis were effectively enhanced. Finally, the mechanical parameters of the rock mass and the initial stress of filed the rock around the faultage F3 in diversion tunnel No. 2 were analyzed.