| Based on the field investigation and data collection and the study of the engineering geological environment conditions of dam area,the engineering geological classification and classification of the rock mass structural surface of Baihe Tan Hydropower Station is carried out.It analyzed the control structure surface of the dam area and conducted systematically study on the development characteristics of the rock mass by employing the three-dimensional numerical model established by the large finite element software.The numerical simulation results of stress field and displacement field under different working conditions are analyzed respectively by simulating the excavation of abutment groove,dam construction and normal water storage,and the stress characteristics and deformation rules of abutment rock mass are studied as well.The main contents and results are as follows:(1)Through field investigation and geological data analysis,we grasp the basic engineering geological characteristics of the topography,stratigraphy,lithology,geological structure,hydrogeology and Geostress in the dam area of Baihe Tan Hydropower Station,and briefly analyze the characteristics of rock mass weathering and unloading in the dam area.(2)Engineering geological classification and categorization of rock mass structural surfaces in dam area and the cause and evolution process of structural plane are discussed,and the development characteristics of structural plane are analyzed in detail.According to the physical and mechanical properties of rock,we put forward the main factors that affect the quality of rock mass.(3)it is to establish a three-dimensional numerical model of dam abutment by using finite element software,according to the design of dam abutment excavation slope ratio of nine step excavation method and to simulate the excavation of dam abutment deformation characteristics of rock mass under stress conditions.The comparison and analysis of simulated values and monitoring data are basically in consistence.According to the simulation results,the excavation process of dam abutment has a certain disturbance on the abutment rock mass,but the stress and displacement caused by disturbance are small,which has little effect on the stability of the abutment.(4)Based on the design data of the arch dam,a numerical model of the dam body is set up to simulate the stress and deformation of the abutment rock under the condition of the dam construction.The results show that the dam construction process has little effect on the stability of the abutment rock mass,and is rather trivial compare with the influence of n excavation disturbance on the abutment rock mass.The deformation of the abutment rock mass is relatively stable mainly on the relatively steep terrain and the weak structural plane.(5)Under normal water storage conditions,the arch dam will transfer the load to the abutment rock mass on both sides of the dam,causing the change of stress and displacement fields of the abutment.The stress and deformation characteristics of abutment rock mass under normal water storage conditions are numerically simulated.The results show that under normal water storage conditions,the total displacement of the abutment rock mass is not large,and the whole body is in a stable state.However,we should pay more attention to the influence of the dynamic water pressure caused by the change of the reservoir water level on the rock mass of the dam abutment,and focus on the geological structure development and the steep terrain. |
