Engineering geological problems related to high geo-stresses at the Jinping I Hydropower Station, Southwest China

The Jinping I Hydropower Station will generate some 3,600 MW. The site of the 305 m high arch dam is in a steep, 1,500-2,500 m deep valley on the Yalong River in Sichuan Province, South West China. The present geo-stresses in the marble bedrock are up to 40 MPa. Relaxation due to river incision has resulted in fractures opening up to 350 m from the rock face. The geo-stresses in the rock mass are significantly affected by the topography. A concentration of stress has developed at the foot of the slope and in the valley floor; it was estimated there would be 132 mm of relaxation/heave of the formation level. The paper discusses some of the engineering geological problems encountered as a result of the high geo-stresses and the mitigation measures undertaken.