Abstract:
Geological conditions of the underground openings of Houziyan hydropower station are complex, i. e. developing of jointed fractured rock mass, being influenced by multiple faults and compressive fracture zones, and being located in the area with middle-high initial stresses. The deformation and damage of the surrounding rock mass are obvious during construction. In order to ensure the safety of construction of works, it is necessary to analyze the stress deformation and stability of the whole opening group during the construction period. Based on the relevant design parameters and support schemes for excavation, a three-dimensional finite difference model is established for the underground openings of the Houziyan hydropower station, and the inversing stress field distribution and the entire construction process of openings are simulated. The analysis results show that with the expansion of free surface excavation, the stress relaxation of the upper and lower reaches of the side wall is more remarkable, and that the stress concentration of different degrees appears in the fault-exposed belt and at the bottom of the machine pit wall. The displacement of the surrounding rock during excavation is gradually increasing; and large deformation occurs at the connecting place of the openings. The supporting scheme can limit the deformation of the surrounding rock mass and reduce the area of the plastic zone, which means that the support scheme is reasonable for the construction of the openings.