Analysis And Evaluation Of Deformation And Failure For Rock Mass In Underground Powerhouse Of Jinping?Hydropower Station In The Dynamic Construction

Underground factory areas of Jinping-I Hydropower Station have dense grottoes, vast scales and complex geological conditions. Surrounding rocks generated large deformations during the construction period of the factories under the combined actions of disadvantaged factors such as faults, high ground stress, unloading of rock mass and so on. As a result, safety during the construction of the underground factories of Jinping-I Hydropower Station was under great threat. Therefore, this article plans to conduct an in-depth study on the deformation and failure characteristics of surrounding rocks of the cavern group of the underground factories. Numerical modeling was employed to analyse the deformation of surrounding rocks in the process of dynamic construction of the underground cavern group, hoping to ensure stable surrounding rocks, safe and economical construction. The major research achievements of the article are as follows:(1) in the excavation process of the main factory in longitudinal fracture surface 0+31.7, layered excavation imposed greater influence on the main factory and downstream side walls of the main transformer room than upstream side walls. Stepped excavation had a smaller influence on cavity deformations of the tail compartment.(2) in the stepped excavation process of the main factory in longitudinal fracture surface 0+126.8, stepped excavation imposed nearly the same influence on upstream side walls and downstream side walls for the main factory, while more influence on downstream side walls for the main transformer room. In addition, the displacement of downstream side walls of the main transformer room would remain increasing.(3) Compared with the monitoring results, in longitudinal fracture surface 0+31.7, the simulation of the location and scope of the rupture zone appeared in the abutment of the main factory fitted the reality, and so did the generation time. Besides, in fracture surface 0+31.7, the simulation of the rupture zones appeared in the lower abutment and hance of the main transformer room is a little bit larger than the pratical zones, while the position and the generation time of the rupture zones coincided well with the results.(4) Compared with the results of field measurements, in longitudinal fracture surface 0+126.8, the simulation of the rupture zones of upstream side walls of the main factory and downstream side walls of the main transformer room fitted the reality.(5) This article and the results of field measurements both indicated that the anchor cables and bolts surrounding the underground cavities overloaded severely. Compared with the overloading of short bolts, the internal force overloading of long anchor cables and long bolts was more serious. Since shorts bolts bring limit restriant to surrounding rock deformations, more long anchor cables and long bolts are needed to restrict surrounding rock deformations.