Seismic Response Analysis Of High Earth-rock Dam Stability Under Excess Pore Water Pressure

In recent years,with the continuous development and utilization of clean energy in our country,several large-scale water conservancy projects have been built and are under construction in China.Earth-rock dams are widely built because of their advantages.In recent years,many earth-rock dams with a height exceeding 200 m have been built in China.However,Southwest of China,where water energy is rich,is located in the border area between the Pacific plate and the Eurasian plate,with frequent seismic activities.so it is particularly important to analyze the stability of the earth-rock dams in areas with high seismic intensity under earthquake action.In this paper,based on the finite element theory of the earth-rock dam,the finite element calculation models of the Nuozhadu dam and the shadow dam are established by using the finite element software Geo-Studio.The relationship among excess pore water pressure,stress and displacement of the high earth-rock dam under the action of pore water pressure,different core forms,different water levels,and different peak accelerations are emphatically analyzed,and eight working conditions are calculated.The main research contents and conclusions of this paper are as follows:(1)The research status of pore water pressure and seismic dynamic response of the earth-rock dam are analyzed,according to seepage calculation theory and soil static and dynamic calculation principle,and the mathematical calculation models of the high earth-rock dam are established.(2)The concept of shadow dam is put forward.The finite element calculation models of high earth-rock dam and shadow dam are constructed by Geo-Studio.The results show that the pore water pressure of the Nuozhadu dam is the same as the pore water pressure of Shadow Dam.With the increase of water level,the horizontal and vertical displacement,maximum principal stress,and minimum principal stress of earth-rock dam increase.Nuozhadu dam has advantages over shadow dam in terms of anti-seepage effect,stress distribution and displacement,which is very suitable to choose a straight core rockfill dam for Nuozhadu Reservoir from the optimization point of view.(3)Under the action of the earthquake,the maximum position of excess pore water pressure is related to the distribution of pore water pressure,and the excess pore water pressure is the largest in the area where the pore water pressure decreases fastest.The maximum effective stress and minimum effective stress of the core wall upstream of the water pressure line with the pore water pressure of 0 gradually decrease with the earthquake,and the upstream and downstream critical interfaces of the core wall are prone to hydraulic fracturing.In the vicinity of the maximum excess pore water pressure,the effective stress decreases obviously,the displacement concentration phenomenon is obvious,and liquefaction and cracks may occur,which should be paid attention to.(4)With the increase of water level,the effective stress decreases.The horizontal displacement and vertical displacement gradually decrease,and the reservoir water has a certain limiting effect on the displacement of the dam body excess pore water pressure has little change.With the increase of earthquake peak acceleration,stress,displacement,and excess pore water pressure stress increase,effective stress decreases,minimum effective stress of upstream and downstream boundary surfaces on core wall decreases,and hydraulic fracturing easily occurs.Excess pore water pressure on the core wall of the earth-rock dam increases,and hydraulic fracturing and liquefaction are more likely to occur at the maximum value.(5)Compared with the Nuozhadu dam,the excess pore water pressure of the shadow dam is larger than the excess pore water pressure of the Nuozhadu dam at the upper part of the core wall,and the excess pore water pressure,stress and effective stress are concentrated near the inflection point at the junction of core wall and filter material of shadow dam,which adversely affects the stability of earth-rock dam.Shadow dam is more sensitive to excess pore water pressure(6)Under the action of the earthquake,the water level has little influence on the Nuozhadu dam,but has a relatively great influence on the shadow dam.The change of earthquake peak acceleration has a great influence on the earth-rock dam.The effective stress at the maximum excess pore water pressure is obviously reduced and the displacement concentration is serious,so we should pay attention to the stability of the junction between the upstream and downstream of the core wall and the height of the 2/3 dam in the center of the core wall Compared with the Nuozhadu dam,the shadow dam is more prone to crack at the junction of the upstream and downstream of the inclined core wall,which proves that the crack resistance of the Nuozhadu dam is better than that of shadow dam.Therefore,the Nuozhadu dam has more advantages than the shadow dam in terms of seepage control effect,stress and displacement,seismic performance,excess pore water pressure and dam stability,which shows that it is very suitable for Nuozhadu reservoir to choose straight core rockfill dam...