High buried depth of Jinping II tunnel lead to sharp contradiction between stress and rock mass strength. The damage zone existing in surrounding rock has important impact on both the tunnel stability and supporting design. Fully understand the damage zone characteristic and damage degree can be used to provide solid and strong basis for supporting optimization design. Based on reorganization on the mable mechanics behavior and damage zone characteristics, establish the research method about deep buried mable in Jinping II tunnel. According to the damage characteristic difference between class II and class III marble, use continuous mechanics method and discontinuous mechanics method to study the damage zone, and obtain the damage zone depth and distribution characteristics. The research result can be directly used to guide anchor length optimization design.
The sharp contradictions between the geostress and rock mass strength will lead to excavation damage zoen (EDZ). The range and distribution of EDZ will threat the surrounding rock stability and construction personnel, equipment safety in deep buried tunnel. At the same time, the rock fracture development in EDZ will form a very good guide water channel. The external water intravasation, internal waters or chemical leakage problem will influence engineering and environmental safety seriously, and affect the tunnel supporting design and cost.
As is known to all, the excavation of tunnel surrounding rock will appear damage and stress redistribution phenomenon, but the real research work about the relationship between the damage to surrounding rock and the stress redistribution is in the 90 s, mainly is Canada URL research. According to a series of comprehensive lab and field tests, in-situ test and analysis research work in URL, the excavation damage zone in surrounding rock is defined as unrecoverable damage by excavation, including the energy release of the impact of the surrounding rock formation damage by excavation methods (such as blasting), stress redistribution and other factors lead to crack propagation such as temperature and humidity changes. Therefore, surrounding rock damage is defined as some permanent change in mechanical and hydraulic characteristics of the surrounding rock, which can be quantitative test Read, R.S. (2004), Martino J.B. and Chandler N.A. (2004), Backblom G. and Martin C.D. (1999).
In Jinping II tunnel engineering practice, the major concern is the influence of damage to rock mass characteristics, surrounding rock stability and supporting security, and focuse on the stability evaluation and engineering way to deal with. In addition, relative to the surrounding rock damage extent in URL, the damage degree caused by stress in Jinping II buried tunnel is more relative serious. So it is necessary according to Jinping II buried tunnel to carry out the research on fracture damage characteristics in surrounding rock to guide the tunnel support optimization design.