Research On Xiaowan Arch Dam's Abutment Stability And Reinforcing Treatment Measures

Arch dam has been widely adopted in worldwide countries for its economy and security. Especially in recent years, concrete high arch dam have a rapid development and become the mostly type of dam of large-scale reservoir and hydroelectric power station【1】. However, arch dam has a stricter require about graphical and geological conditions than any other type of dam. The stability of dam abutment should has a direct relation to failure-free operation and security of projects,and security of downstream people's life and property as well. According to incomplete figures, threr were 45 cases caused by spoil and other security accident about constructed arch dams in the world, among them 28 cases were caused by abutment destabilization, which account for 62% of them【2】, so the arch dam genuine potential hazard lies in the stability of side banks dam abutment rock mass. Therefore, abutment stability analyses and foundation treatment are the key to success in constructing arch dam or not. Xiaowan arch dam site has excellent topographic conditions, while geological structures in both abutments are complex, such as, faults, altered rock, mantle rock, etc. The operation and stability of dam-abutment system will be decreased by asymmetrical displacement in both abutments, increasing compression deformation and bearing capacity limit of abutment. Obviously, it is wise to analyse abutment stability before building so high arch dam in complex geological dam site. Firstly, by evaluating abutment stability accurately, studying displacement and its distributing features of dam abutment, analyzing failure pattern, process and mechanism, measures are put through. Secondly, by studying the strengthening case, that abutment rock distributing features of stress and displacement, abutment stability, and project's reliability can be improved. In connection with EL.1210m plane of Xiaowan project, geomechanical model test combining finite element method is principaliy adopted to study the stability of dam shoulder and foundation and the rationality of reinforcing treatment measures. several research findings are made as follows: (1) initial case: the overloading safety factor Kp of dam shoulder and foundation of EL.1210m plane of Xiaowan project is 2.2(geomechanical model test) or 2.6(finite element computation ); the case of foundation treatment: the overloading safety factor Kp is 3.9(finite element computation ), and the security of the engineering and the rationality of strengthening measures are evaluated; (2) the destruction process, destruction condition and the failure mechanism of dam shoulder and foundation are analyzed and the weakness of the project is concluded. Thus suggestion of reinforcing treatment are proposed; (3) the distribution of displacement and its changing character of two dam shoulders are concluded and the distortion of the dam shoulder and foundation is realized; (4) the distribution of relative displacement and its changing character of the fault and alteration are concluded and distortion of the main geological structure is realized; (5) the distribution of displacement and strain and their changing characters of the dam body are achieved. Important gists are given to the design and construction by this paper..