Abstract： Taking a large-scale underground cavern of hydropower station for example, a 3D numerical model was established to obtain the deformation characteristics of the surrounding rock mass after excavation of the cavern, and the influence of prestress loss of the anchor rope on the surrounding rock mass deformation and stress state was analyzed. The rationality of the simulation method and the feasibility of the support measures was analyzed by comparing the simulation results with the measured results. The results show that the max horizontal displacement occurs at the middle of the sidewall, while the max vertical displacement occurs in the top of the arch, and in the intersect area of the cavern the deformation is significant. The simulation results are very close to the measured results which can show the actual excavation process and the deformation characteristics of the surrounding rock mass. The horizontal displacement  significantly increases when the prestress loss in anchor rope comes to a certain degree.
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