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Abstract A double-curved arch dam is located in Jinshajiang River with a maximum height of 277 m. The excavation height of the left dam abutment is about 300 m，and the right is about 480 m. Because the excavated slopes are high and steep the stability of the slopes has great influence on dam operation and safety. After a detailed analysis of dam site geological data，the 3D elastoplastic finite element model of dam abutment slope is established. And according to the unloading rock mass mechanics theory，the degree and areas of unloading can be gained by contrasting the initial stress field with the field after excavation. Then the degree of rock mass quality deterioration after excavation can also be achieved. With the progress of excavation，the areas and degree of unloading change constantly. Thus in order to study the dynamic stability of the high slopes，the rock mass mechanical parameters are adjusted continually according to the changing areas and degree of unloading after each excavation step. The results show that except partial regions near excavation surface，the abutment slopes are stable during and after excavation processes. After taking the effects of dynamic unloading into consideration，the displacement and plastic zones of slope rock mass after excavation decrease；and the rock mass failure regions change with the course of excavation. According to the distribution of unloading regions and plastic zones after each excavation step，the optimized reinforcing measures can be reasonably selected.
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Received: 20 April 2007
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