水电站地下洞室群分步开挖的非连续变形分析

利用大岗山水电站的地质勘探资料建立不同贯穿节理组合下地下洞室群的DDA模型，分析了洞室群开挖的破坏模式，并简单阐述其破坏机制。基于Monte-Carlo方法模拟节理的随机分布，结合大岗山水电站的开挖设计方案，对地下洞室群在分步开挖过程中的位移及应力演化进行研究。研究表明：洞室群开挖完成后，洞周块体的位移均指向洞内，尾调室上下游与主厂房上游的变形较大；洞周块体的大主应力均平行于洞室边界线，尾调室的应力释放比较明显，其边墙块体发生了滑移；洞室群在开挖过程中互相影响，其中主变室受主厂房和尾调室的影响比较明显。研究结果指出了洞室群开挖过程中需要关注和加固的具体部位，为工程支护措施的优化提供了依据。

Stepwise excavation process of underground caverns of hydropower station using DDA

A process of continuum excavation has been simulated using discontinuous deformation analysis (DDA) which is introduced element birth and death method. Comparing the calculated result with finite element method, we prove that DDA method is effective in cavern’s simulation. Based on the geological exploration data of Dagangshan hydropower station, DDA models of the underground cavern group with different combinations of joints are established. We analyze the failure modes of underground cavern group’s excavation, and explain the failure mechanism briefly. Based on Monte Carlo method and excavation design of Dagangshan hydropower station, random distribution of joints is simulated; and developments of displacement and stress are researched in the sub-step excavation process. Studies show that: displacements of all the blocks around the cavern are pointing to the cavern when excavation is completed; deformations of tailrace surge chamber and underground main powerhouse’s sidewall are relatively large; major principal stresses of the blocks around the cavern are parallel to the caverns’ boundary line; stress of the tailrace surge chamber relieves obviously; and blocks of sidewalls have slid; the three caverns interact on each other in the excavation process; the effects of tailrace surge chamber and underground main powerhouse on the main-transformed cavern are more obvious. The study shows specific parts which are need to be reinforced in the excavation process; and it provides a basis for optimal support measure of the project.