| Distribution of initial ground stress and the sliding stability of rock mass of arch dam abutment are the important factors for design and construction of hydropower projects, also, these are the main problems related to the safe operation of dam. In this paper, we take Baihetan hydropower station as research object, by analyzing the field geologic data, this paper study the regional geologic background, topography and landforms, stratum and lithology, geological structure, evolution of river valley type and rock mass structure, the characters of regional tectonic stress field etc. Based on these researches, three dimensional numerical model of dam area has been established by using numerical simulation methods; initial ground stress field of arch dam was simulated and analyzed by means of the FLAC3D software. At the same time, based on studying the structure of rock mass, geological structure, arch dam abutment resisting force body, we have evaluated and analyzed the stability of arch dam abutment on the condition that excavation of the spandrel, respectively, damming process, under normal load conditions of the dam body resistance. The specific content and research results are as follows:(1) Through field geological data analysis and demonstration, we have a in-depth understanding to the topography, lithology, geological structure and other engineering geological conditions on the Baihetan hydropower station dam area, also make preliminary analysis to the tectonic stress field of dam area, as well as formation and evolution of valley. A preliminary analysis about the characteristics of stress field of dam area has been done According to the measured stress value on the stress field(2)In this paper, we carried out engineering geological classification on structural surface of rock mass, quantitative, semi-quantitative description and analysis for all levels of engineering geological characteristics of the structure surface have been done. At the same time, we also have made a focus of analysis to the crucial controlling structural surface(3)In the third chapter, we analyzed the model and character of deformation failure of dam abutment rock mass, to determine the bottom sliding surface and sideslip surface, and made a detailed analysis to the engineering characteristic of intrastratal or interbedded disturbed belts and major faults.(4)we have analysis to the formation and evolution of river-valley landforms of dam area, generalization the downcut mode and number of periods of the valley, also establishment three-dimensional geological model of the dam area. Using FLAC3D numerical calculation software, based on the measured data of ground stress, the back analysis for initial stress field of dam area has been done.(5) Through engineering experience analogy method to select slope ratio of dam abutment excavation, this paper established the excavation model of dam abutment, calculation and analysis the stability, stress changes of dam abutment resisting force body under the conditions of excavation of dam abutment. The results show that, the process of excavation unloading, there exists a certain disturbance on the dam abutment resisting force body, but, the effect is very little. In the exposed parts of weak structural surface with poor engineering properties, the larger displacement of local is unable to affect the general stability of dam abutment resisting force body.(6) Established the dam model according to the dam design parameters, to calculate the deformation stability and stress changes of dam abutment resisting force body in the course of step-by-step building the dam. The turbulent influence to resisting force body in dam loading process is very small; the dam abutment resisting force body is stable.(7) To analyze the deformation stability and stress changes of the dam abutment resisting force body under the normal load condition. The results show that,under normal work load,the overall features of abutment rock mass deformation of Baihetan Hydropower station shows that the rock mass deformation on the left bank of abutment is greater than the right bank evidently, the total displacement is smaller, and the arch end displacement consistent with the general law,therefore, as a whole,under normal work load of dam,we think the abutment rock mass is stable. At the same time,shift mutation phenomenon appear in the fault zone,fault's development site,which may lead to the problems of local stability is lower. these should be the main problem in construction process.
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