The complex geological conditions and rock mechanics environmental changes in the dam area directly affect the abutment stability of rock against sliding and the safety of arch dam. In Southwest China

the dam area of Wudongde ultra-high arch dam has extremely complex engineering geological conditions. After the dam is unloaded

the nature geological conditions become the main factors to affect the abutment stability

such as formation lithology

fault structures

karst system

skewback discontinuous fissures. Based on the geological exploration data

two-dimensional geological sections and engineering data of the feasibility study stage

the object-oriented technology

and a variety of collaboration software are used to establish a geometric model of the natural geological conditions and engineering objects. Finally

a three-dimensional fine finite element model which is suitable for the analysis of the abutment stability is built under the conditions of inversion analysis of ground stress

the dam load

exaction and so on. The three-dimensional fine finite element model simulates the complex structure of engineering largely

which provides a good foundation for the comprehensive analysis of the stability of high arch dam abutment rock. The results show that stress level of both the near-surface ground stress zone on both sides of the valley and deep ground stress zone of riverbed is close to the actual measured value. After the excavation of dam abutment is completed

the maximum displacement reaches 12.9 mm near the right bank of 800 m elevation of spandrel groove. There are some differences in the 9 sliding blocks under the different loading combination conditions; and the stability of the left abutment is stronger than that of the right on the whole. Under the combinations of seismic loads

all safety factors of the wedges will reduce largely; but there is still some margin of safety.