(1. HydroChina Huadong Engineering Corporation，Hangzhou，Zhejiang 310014，China；2. HydroChina Itasca Research and Development Center，Hangzhou，Zhejiang 310014，China)
Abstract：The marble of Jinping II hydropower station diversion tunnel shows a phenomenon of crack propagation with time under high geostress，which impacts significantly the run-time safety of diversion tunnel. The lag fracture after excavation，monitoring results by bolt stress meter and sound wave test all reflect the characteristic of crack propagation with time. The laboratory test and numerical analysis are adopted to prove that the fracture is the main response way of marble after excavation，which indicates that a bolt stress meter and sound wave test have better applicability，and multipoint displacement meter sensitivity is worse. The behavior of GSI decreasing exponentially with time is used to stand for marble strength decreasing with time，and further behalf on tunnel excavation damage zone increasing with time. Based on the theory，the stress corrosion(SC) model is set up. The obtained field monitoring and testing data are used to check the related parameters of SC model. The long-term mechanical response of marble，anchor stress state and lining structure security are analyzed in detail；and these characteristics consist well with the actual excavation response.
SCHMIDTKE R H，LAJTAi E Z. The long-term strength of Lac du Bonnet granite[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1985，22(6)：461-465.
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2013, Vol. 32 
