Guaigui multipurpose project rock slope stability

The construction of the Guaigui Multipurpose Project includes a 74 meter high concrete face rock fill dam, a 350 meter long diversion tunnel and a 350 meter long spillway tunnel. The topography in the project area is very steep, and the rock masses are characterized as soft rocks. The stability of the 80 to 100 meter high dam abutments and the excavation of the tunnels in soft rock conditions have caused various challenges and problems to be solved. Limited pre-investigations have called to a great extent for estimation of parameters for the stability calculations. The preliminary calculation of the stability of the planned rock slope above the spillway intake platform has been carried out by conventional partial factor method and by use of computed based Slide Program. The calculation gives different results for the two methods, and indicates that rock support is necessary to obtain an acceptable factor of safety for a slope inclination of 52o. The input parameters for the rock mass characteristics need to be verified for the permanent calculations.