Seismic Analysis For Underground Powerhouse Structure Of Hydropower Station

With the vigorously implement of the western development strategy and the continued advance of west-east power transmission project in China, a large number of giant hydropower stationswhich have world-class unit capacity are being built or designed. Most of them are in high intensity earthquake zone and are in the form of underground structures. Because of their big structure size, huge excavation scale and relatively low stiffness, it makes the strength, vibration and stability problems of the powerhouse increasingly prominent. In hydropower engineering, for a long time, it is considered that the seismic performance of underground powerhouse is superior tothe ground one. It will meet the seismic requirements for hydropower station underground powerhouse when referred to seismic design law of the general industrial powerhouse. But the damage on the underground powerhouse has been reported in many literatures and many scholars are calling for that the seismic research of underground powerhouse structure should be emphasized and strengthened.However, in the existing seismic analysis of underground powerhouse, most of researches all put their analysis emphasis on the seismic response of underground powerhouse cavern group and pay less attention to the powerhouse structure. So far, there is still no underground structure seismic design code in our country. The main reasons are that the basic research work carried out is not enough, and that the related information accumulation is insufficient, and that the systemic research and seismic design method for the dynamic responses of underground structures is severely lacking.So, the research on earthquake reaction mechanism and seismic performance of underground powerhouse of the large hydropower station is both necessary and of extremely important significance.In view of the problems existing in the seismic research of the underground powerhouse structure, a three-dimensional finite element model is built in this paper.The modal is based on viscous-spring boundary.theory and equivalent seismic load input method and the explicit dynamic finite element analysis software of LS-DYNA, and finally it is to analyze the seismic response of underground powerhouse. Following are the main works of this paper.(1) Based on the finite element analysis software, the time-history analysis method is used to calculate seismic response of underground powerhouse structure. By analyzing the seismic response, such as the displacement, acceleration, stress and inter force of the main parts of the powerhouse structure, the seismic response law of underground powerhouse structure is known.(2) A method is applied to calculate the static and dynamic combination effect of underground powerhouse structure by explicit dynamic finite element. Compared with seismic response while the structure is under the function of the seismic load, the influence of static load on seismic response of the underground powerhouse structure is investigated.(3)The inner force of the upstream and downstream side columns is larger than the other columns by analyzing and comparing. The analysis and comparison is conducted between the inner force of columns only under seismic load and that under both static load and seismic load. To research the effects of connection type between surrounding rock and columns along the upstream and the downstream sides on the seismic response of underground powerhouse, two seismic response are calculated when the structure is only under seismic load and under both static load and seismic load.The results indicate that, separating the upstream and downstream side columns from the surrounding rock is beneficial to reduce the seismic response of underground powerhouse structure.