| China’s dam construction is mainly located in the southwestern hydropower resources,a large number of high arch dams and high gravity dams have been built,and some dams are under construction or will be built soon.At the same time,these areas are also earthquake-prone areas in China,and the seismic intensity is high.Therefore,the principle of ensuring the seismic safety of the dam runs through the whole process of site selection,design,construction,operation and maintenance of the dam.For horizontal stratified foundation of gravity dam,this thesis established considering the influences of soil-structure dynamic interaction is able to time domain dynamic analysis method,and according to the foundation excavation and concrete replacement two bad quality under the condition of processing dam foundation treatment method,analyzed the dam response,the layers for horizontal seismic responses of the dam foundation in gravity dam and the different provide preliminary technical basis for the selection of foundation treatment measures.The main contents of this thesis are:(1)Time domain ray tracing stepwise recursive method is used to solve the time domain free field response of layered soil.The viscoelastic artificial boundary condition is used to simulate the phenomenon of wave motion generated by dam vibration to infinity and the corresponding ground motion input model.Therefore,a gravity dam-foundation system dynamic interaction analysis method capable of approximating the radiation damping of an infinite foundation is established.(2)According to the foundation treatment method of foundation excavation,the influence of different excavation depths on the dynamic characteristics and dynamic response of gravity dam under layered site conditions is studied by adjusting the elevation of the foundation surface.(3)According to the ground treatment method of concrete replacement,the effects of different displacement depths on the dynamic characteristics and dynamic response of gravity dam under layered site conditions are studied.(4)The analysis results show that:(a)For the horizontal free-field conditions studied,when the SV wave and the P wave are respectively perpendicularly incident,in the low frequency range,at the interface of each soil layer in the 15 m region below the surface The acceleration response spectra are not much different,but in the high frequency range,there is a big difference,and the ground stratification has a significant impact;(b)For the foundation treatment method for foundation excavation,as the depth of the foundation is increasing,the height of the dam is also increasing,the fundamental frequency of the structure is decreasing,and the rate of change is getting smaller and smaller.In the whole process of action,the vertical stress of the dam and the maximum of the first principal stress and the minimum of the third principal stress are distributed on both sides of the dam,the upstream surface is close to the dam heel,the downstream surface is close to the dam toe,and at each depth the stress and displacement are different but not much different.For the foundation treatment method of concrete replacement,the stress field and displacement field of the dam body will be divided into two processes.When the local base displacement depth changes within a certain layer of foundation,the stress and displacement of each key point will fluctuate.When the displacement depth changes within each layer of the layered foundation,the tensile stress and compressive stress of the dam and the dam site decrease,the stress of the corridor increases,the relative displacement of the dam decreases,and the tensile stress zone of the horizontal plane will increase. |
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