3-D Dynamic Analysis Of High Rockfill Dam In Meizoseismal Area

Earth-rockfill dam is widely used because of its features such as simple structure, economy and quick construction. With the rapid development of hydraulic and hydroelectric construction projects in China, the height of proposed rockall dam has reached 300m. The geological condition in western areas is complex and earthquake there is frequent and strong. Therefore seismic study of dam is becoming more urgent and important. It has been found that seismic damage of dam is closely related to acceleration amplification. Seismic damage will occur on earth-rockfill dam once seismic acceleration amplification is beyond a certain range. So it is significant to calculate three dimensional dynamical response of high earth-rockfill dam in highly seismic region, to study distribution of acceleration amplification and to determine range of seismic-strengthening.This paper takes highly seismic region as background and applies equivalent viscoelasticity model to analyze three dimensional dynamical response of homogenous rockfill dam under various working conditions. The work of this paper is as follows:(1)This paper calculates and analyzes effect of meshing size to seismic response of high homogenous rockfill dam which is 100 meters, 200 meters and 300 meters high. It also includes research on effect of meshing size to calculation accuracy of dam dynamic response based on calculation of three dimensional dynamical response. Valid height of grid is discussed and determine. A conclusion is drawn that meshing size have an obvious effect on acceleration amplification and meshing size should be determined firstly by pilot calculation before three dimensional calculation is carried out. The results show that valid height of grid is 5 percent of that of dam to homogenous dam within 300 meters high.(2) The paper also calculates and analyzes dynamic response of high homogenous rockfill dam which is 100 meters, 200 meters and 300 meters high in various working conditions. Research on distribution rule of acceleration amplification of dam is done. Range of seismic-strengthening is discussed and determine. And conclusion is draw as follows: the area of acceleration amplification of dam is elliptic; the influence of acceleration amplification along and above 4/5 height of the dam is obvious; the influence of acceleration amplification which centers on center of top dam and is within 3/10 areas is obvious. The higher the dam, the steeper the dam slope is; the wider the stream valley, the smaller the dynamic sheer modulus and acceleration amplification are. All above is about relationship between acceleration amplification and features of dam. Acceleration amplification is also in connection with seismic input. The larger the seismic dynamic input, the smaller the acceleration amplification. And seismic response varies by different seismic wave.