Study On Dynamic Response Characteristics Of Reservoir Bank Slope Under The Influence Of Reservoir Earthquake And Water-Rock Interaction

A large number of bank slope rock masses are formed in hydropower engineering construction.Reservoir earthquake not only causes irreversible progressive damage to slope rock masses,but also acts as a dynamic action of cyclic loading and unloading.On the basis of theoretical analysis,the Zigui section of the three gorges reservoir area,where reservoir earthquakes occur frequently,was selected as the key research area.Based on the study of the reservoir earthquake expansion and migration law,the author analyzes its seismic mechanism in the research area.The typical sandstone in the reservoir bank slope subsidence zone of the three gorges reservoir area is selected as the experimental research object.The related water-rock interaction test and theoretical research are combined to reveal the seismic dynamic characteristics deterioration and the dynamic response mechanism of the reservoir slope.Firstly,water-rock interaction test and dynamic cyclic loading and unloading test were carried out to explore the damage and degradation rules of sandstone dynamic characteristics under cyclic dynamic damage and long-term water-rock interaction.Secondly,based on the physical characteristics and its microstructure change characteristics of rock samples,the degradation mechanism of rock mass dynamic characteristics under water-rock interaction is analyzed.Finally,by means of numerical simulation,the dynamic response characteristics and mechanism of bank slope under water-rock interaction and seismic damage are studied.The main research results are as follows:(1)With the rising water level of the reservoir,the seismic activity in Zigui reservoir shoreline of the three gorges reservoir area experienced a process from weakness to stronger and then gradually weakened.Seismic activity occurs near the boundary of Xiannvshan fault and Jiuwanxi fault.Most of them are of low magnitude,and reservoir earthquakes are characterized by high frequency and low intensity.Reservoir earthquake belongs to a tectonic "trigger" earthquake,and its seismic mechanism is mainly affected by the tectonic characteristics of faults and pore water pressure effect.(2)As the water-rock period increases,the damping ratio of sandstone increases,and the damping coefficient and dynamic modulus decrease obviously,and its change law can be fitted by logarithm function.Similarly,the damping ratio of the damaged rock sample increases,the damping coefficient and dynamic modulus also decrease,and the change rule can be fitted by quadratic function.In comparison,under the same degree of water-rock interaction,the periodic dynamic damage has obvious influence on the dynamic characteristics of rock mass.(3)With the increase of water-rock interaction period,the density and wave velocity of rock samples show a certain decreasing trend,and the porosity appears increasing trend.In comparison,the physical parameters of rock samples under cyclic dynamic damage and cyclic water-rock interaction vary the most in each water-rock period,followed by initial damage and cyclic water-rock interaction,and the rock samples under cyclic water-rock interaction are the least.From the microscopic point of view,the water-rock interaction has obvious damage effect on the rock structure.Under the influence of dynamic cyclic loading and unloading damage,the cumulative effect of microscopic damage is more obvious.(4)Without considering the water-rock interaction,the dynamic response of the bank slope is a typical amplification effect at the top.With the increase of water-rock interaction period,the dynamic response of slope hydro-fluctuation belt zone increases gradually,and that of other parts of slope decreases gradually.In the first 6 water-rock interaction cycles,the dynamic response of each part showed an obvious variation trend,and by the 8th and 10 th water-rock interaction,the dynamic response of each part tended to be stable,indicating that the influence of water-rock interaction on the slope dynamic response was significant.In comparison,the overall dynamic response of the slope is relatively small when the reservoir water level is 145 m.Under the same reservoir water level,the slope dynamic response is more obvious under the condition of periodic water-rock interaction and periodic dynamic damage.