Back Analysis And Stability Assessment For Laxiwa Underground Powerhouse

It's very difficult to accurately determine the mechanics parameters of the caves, the boundary and initial conditions, the best construction scheme and support parameters before the caves are excavated, so there are a lot of blindness, diseconomy and hidden risks in the predesign of the caves. Based on the displacement measurement during the excavation process, the initial stress and mechanics parameters of the laxiwa underground powerhouse are studied by the back analysis. Finally, the parameters by back analysis are used to predict the stability of surrounding rock mass of the caves during the later excavation. The major results in this paper can be summed up in following:(1) According to the regression and back analysis, the initial stress of laxiwa underground powerhouse has been achieved, the three-dimensional distributing rule for initial stress is proposed, and is used in the later analysis, the stress data between the calculation and the measurement show a good coherence ,which proves the feasibility of the simulation method.(2) Through change the k(modulus of horizontal stress)and the h/b(high to span), this paper gives a systemic research on the deformation rule and plastic region by establishing a dynamic multi-step finite element model to simulate excavation process of laxiwa underground powerhouse.(3) On foundation of the excavation, displacement and deformation rule, the deformation and strength parameters of different areas are proposed in the back analysis.(4) Aim at the characteristic of laxiwa underground powerhouse, the estimate methods and standard are given in this paper.(5) Finally, the results of back analysis are used to predict the stability of surrounding rock mass during the later excavation; the prediction analyses results indicate that the whole stability of surrounding rock of underground powerhouse is relatively good.