巴基斯坦尼拉姆—吉拉姆水电站地下厂房围岩稳定反演分析

为了反演尼拉姆—吉拉姆水电站地下厂房开挖及支护过程,分析施工中出现问题的原因并给出优化方案,结合工程施工期安全监测资料及地质资料,采用通用岩土分析软件MIDAS GTS NX,考虑材料非线性、不同岩性材料分区及软弱夹层地质构造的影响,选取摩尔库伦本构模型对地下厂房、主变洞室及母线洞、尾水洞开挖支护过程进行有限元模拟,提出优化结构方案并对其进行验算。结果表明:反演计算结果与现场监测资料基本吻合,软弱夹层对围岩收敛变形及应力分布有较大影响;采用优化方案后,模型最大位移分布区域较初始模型有所减小;初始模型塑性区为洞室跨度的0.57倍,优化后塑性区降为洞室跨度0.4倍。研究成果可为类似地下厂房设计提供参考。

Inversion analysis on surrounding rock stability of underground powerhouse for Neelum-Jhelum Hydropower Project in Pakistan

In order to make an inversion calculation on the excavation and supporting process of the underground powerhouse for Neelum-Jhelum Hydropower Project，the causations of the problems from the construction are analyzed herein，and then the optimized scheme is given out. Combined with the data of the safety monitoring during the construction of the project and the relevant geological data，a proper constitutive model is selected for the finite element simulation made on the excavation and supporting processes of the underground powerhouse，main transformer chamber，busbar tunnel and tailrace tunnel with the general geotechnical analysis software——MIDAS GTS NX under the considerations of the influences from material nonlinearity，subzones with different lithologic materials and geological structures of weak intercalated beds，thus an optimized structure is proposed and the relevant calculation is made on it as well. The result shows that the results from the inversion calculations are basically coincided with those from the in situ monitoring data and the weak intercalated bed has a larger influence on both the convergent deformation and the stress distribution of surrounding rock. After the optimization of the structure，the maximum displacement distribution zone of the model is reduced somewhat，if compared with that from the initial model. The plastic zone of the initial model is 0.57 times of the cavern span，which is decreased to 0.4 times of the cavern span after the optimization. The study result can provide reference for the similar overseas hydropower project.