Three Dimensional Dynamic Stability Analysis Of High Rockfill Dam

Energy has been a main problem that restricts the rapid development of the national economy and society. As a kind of clean energy, hydropower develops rapidly in China. Along with the development of the West Regions, West-East electricity transmission project, South-to-North Water Transfer project are under way, there are more and more constructions of high dam and giant reservoir coming up. Our country's hydropower energy is centered mainly in western and southwestern regions, where are coincidentally meizoseismal areas in our country. The rockfill dam takes up a great proportion in high dam. What's more, the basis of dam security is stability analysis of slope.Although the limit equilibrium method has many advantageous, it is still not mature when dealing with three dimensional stability analysis problems. Compared with it, the finite element-strength reduction technique is more convenient when doing so. FLAC3D analysis software is used as the main calculating tool in this thesis. The strength reduction technique is applied to analyze the factor of safety and the location of the critical slip surface in two kinds of dams, which are concrete faced rockfill dam and clay core wall dam. The work of this thesis is as follows:(1) The location of the critical slip surface. With the strength reduction technique, only a factor of safety can be obtained directly, and the critical slip surface is usually determined through more analysis. There is a new approach for searching the critical slip surface based on equivalent plastic strain in the two-dimensional slope stability analysis, and this thesis extends this method into three-dimensional case. Once the slope is led to the limit equilibrium state by means of the strength reduction technique, a plastic zone will go through the slope from the toe to the top. Along each of the vertical lines in some planes, the point with the maximum equivalent plastic strain is sought out in this study. All of these points form a functional data. Lastly, these control points could constitute a smooth surface by the NURBS method and the least square method, and then the critical slip surface will be built.(2) The factor of safety is calculated by means of pseudo-static method under circumstance of different height of dam, gradient of slope, earthquake intensity as well as shape of valley. Of course, the location of critical slip surface is analyzed as well. Through analysis, a result is concluded that the higher dam is, the steeper slope is, the greater earthquake intensity is, the wider valley is and the smaller safety factor is. What's more, the factor of safety has a linear relation with the gradient of slope and a non-linear relation with the other elements. Through the result, an empirical correlation is provided in this thesis. And it's found that earthquake intensity has a great effect on the location of critical slip surface. The location of critical slip surface ascends gradually to dam crest with the increase of earthquake intensity.(3) A pseudo-static method is also used to study the dynamic stability of clay core wall dam under different circumstances, and the location of critical slip surface is also analyzed. By analyzing the stability of slope, it is known that the effect of height of dam, gradient of slope and earthquake intensity on safety factor is similar to concrete faced rockfill dam, but the location of critical slip surface is deeper, and about 1/5 height of the dam.