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Abstract Aiming at the deformation and cracking phenomena of surrounding rock mass during the excavation of Jinping I hydropower station underground powerhouse under the conditions of high stress and low strength stress ratio，the characteristics and laws of in-situ stress field are studied entirely by the stereographic projection method and projection stress on typical planes. The deformation and cracking mechanism of surrounding rock of underground caverns group are deeply analyzed through mechanical qualitative analysis and 3D numerical simulation；and the damage evolution law of surrounding rock is studied. The results show that the relatively large deformation and cracking phenomena of surrounding rock and shotcrete layer of underground powerhouse are caused essentially by the adverse combination of the high ground stress and relatively low rock strength. The cracking failures in haunch，arch abutment and side wall of main powerhouse and main transformer chamber，and in side wall of busbar tunnels are typical unloading deformations and failures under the conditions of high stress，low strength stress ratio. The generalized model of surrounding rock deformation and cracking of underground powerhouse is presented. It affords important reference and qualitative basis for the back analysis of in-situ stress field and the numerical simulation of excavation process. Finally，some advices are given to maintain the stability of surrounding rock mass. All the results afford technical support to the construction and dynamic support design of the underground powerhouse.
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Received: 02 June 2010
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2010, Vol. 29 
