Study On Stability Of Surrounding Rock And Optimization Of Bolt Parameters For TBM Assembly Cavern In High Stress

With the fast economic development of china, many more constructions were carried on in the field of the hydro electric power, water conservancy, railway, highway and mining. The related underground tunnel tends to be deeper and longer and larger. It was verified by a mount of engineering constructions that the presence of high in-situ stress was the important factors that influence the stability of the high deep tunnel. Abundant researches on the surrounding rock stability of the tunnel subjected to the high in-situ stress were carried on in domain and abroad. Most of the analysis was focused on the separated engineering construction. The comprehensive analysis system on the surrounding rock stability, failure modes and the building program decision was in lack. The surrounding rock analysis results from the ordinary conditions methods can not conform to the practical status, especially in opposite.In this paper, based on the excavation of the TBM assembling tunnel in the No 3 hydropower tunnel of JinPing second level hydropower station, studied that the deformation of the surrounding rock and the distribution of stress under the situation of high in-situ stress. Through a multi-index analysis and comprehensive evaluation to determine the reasonable excavation method and the bolting parameters of the tunnel. This article reads as follows:(1) Based on the knowledge of the regional in-situ stress forming conditions and influence factor, the compute method on the regional in-situ stress was presented. The 3D in-situ stress inversion was analyzed with regression method in definite element model. The necessary technical preparing for the numerical stability analysis of the tunnel subjected to the high in-situ stress was afforded.(2) The damage characteristics and evolution procedure of the surrounding rock in high in-situ stress condition is apparently different from in ordinary geology conditions. Considering the damage characteristics and rules of the surrounding rock in high in-situ stress, the surrounding rock stability indexes were presented such as the surrounding rock stress relax ratio symbolizing the failure level, surrounding rock safety ratio, damage domain, energy transferring and release ratio. Further more, the fractional average energy release rate; a new forecast index of the rock burst was afforded based on the energy release disciplines. The comprehensive analysis system including the surrounding rock stability, rock burst and program optimize was concluded based on the multi goals optimize method.(3) Based on the excavation of the TBM assembling tunnel in the No 3 hydropower tunnel of JinPing second level hydropower station, systematically carried on stability analysis of underground with different excavation programs and excavation footage. Through the value of fractional average energy release rate,conducted rockburst exploratory study. Finally, a reasonable plan of excavation and excavation footage has been determined by the evaluation of multi-index.(4) Underground support parameters are determined according to the engineering analogy. In this paper, a numerical simulation study is established about the TBM cavity for bolting parameters. We analyze the impact of rock stress, deformation, plastic zone and the scale of Rock Burst with the change of the length of the bolt and prestress. According to the evaluation of multi-index, the reasonable parameters of bolting are determined.