ANALYSIS OF ARCH DAM′S ABUTMENT STABILITY UNDER COMPLICATED GEOLOGICAL CONDITIONS AND STUDY OF INFLUENCE OF DENSE JOINTS

According to the geological defects in abutment of Xiaowan arch dam,the plane geomechanical model test based on overload method was carried out to research the abutment stability of typical elevation 1 210 m. In the test,the main fault,altered zone,soft rock zone and the two groups of joints tending to SN and EW were simulated,and the displacement and strain of the dam,the abutment displacement,the failure process,failure modes,as well as the overloading safety coefficient were obtained. So the dam abutment stability could be evaluated. As the result of geomechanical model test was an experimental method,which was based on the principle of geometric similarity and the mechanical similarity reduced the scale of dam and foundation,the model can not simulate the dense joints contained in abutment rock. In order to analyze the influence of the dense joints, the nonlinear finite element method was adopted to research abutment stabilities with and without dense joints. The results show that the impact of displacement of dam and abutment is about-8%–10%,and the impact of overload safety coefficient is about-9%. Therefore,even the model test could not simulate the dense joints contained in dam abutment,the impact of the dense joints in the abutment at elevation 1 210 m of Xiaowan arch dam is small,and the results of the model test are reliable.