Study On The Stability And Seepage-stress Coupling Damage Behavior Of Tunnel Surrounding Rock

The study of structural security and stability started with the underground projects. Around the complexity geological environment, tunnel surrounding rock always lies in a dynamic equilibrium for some natural conditions changing. That some tunnel disasters instability occurring frequently along with excavation and operation bring great loss to the country's economic development and people's lives and property. At the saturation state, the seepage-stress coupling theory, one of the most important coupling contents, was studied and obtained great richly achievement under the interaction between tunnel rock and its environment factors. However, as most results being limited to analysis the macro-cracks in the stress-strain state of rock, there were several shortages such as the new breakdown crack, expansion and penetration process, the permeability evolution process and the damage-permeability coupling process etc. At the same time, the permeability evolution mechanical mechanism is not clear in the breakdown crack process. So there are some things to do in coupling area. In this paper, the seepage-stress coupling damage behavior of tunnel surrounding rock is studied which can understand the surrounding rock mass deformation mechanism, provide scientific and technical support for tunnel alignment layout and excavation, enhance prediction capabilities of the tunnel disaster response and disaster prevention, ensure safety and save investment significant.The main efforts and conclusions results gained can be expressed as follows.1. The stress characteristics of tunnel structure is studied because tunnel excavation would produce rock stress changes. Based on statistics and experiment information, the load distribution rule of tunnel rock and support structure has been analyzed. That tunnel rock is the main source of load and also endures certain load. It has a certain self-stability function in different rocks. So the study on tunnel surrounding rock stability must be explored from some coupling factors.2. On the basis of seepage laws in the tunnel rock, the self-adaptive seepage model (SSM) was established. The SSM can automatically select the appropriate seepage function which descript the different fluid traits in rock according to the seepage medium permeability, and also express the different fluid modes for the seepage speed or the load change. According to the rock permeability theory model, the main physical rock characteristics is studied at the external environment factors.3. The rock damage statistics theory is used on the deformation and crack process. In order to express that yielded and cracked rock has still received a certain load, the tradition statistical damage modification was amended and a new statistics seepage model function was established, which can influence the real rock state. That the amending damage variable parameter and statistics distribution parameters decided the damage equivalent elastic modulus and the curve figure of statistics seepage model function simulate the micro-crack evolution process and some micro-cracks' load effect each other in rock. In new model, variable parameters were calculated by mathematics curve combining with Compositely Genetic Algorithm (CGA). Numerical example shows that the result is efficient and reliable.4. Based on some reasonable assumption, the seepage field and stress field equations have been derived through continuity equation, momentum conservation equation, rock statistical damage amending equation and some substantial equations. Then the seepage-stress coupling damage behavior model is established in saturation state.5. According to some initial and boundary conditions of tunnel surrounding rock, the finite difference method is explored in seepage-stress coupling damage behavior model.6. Hierarchical pattern search is provided to solve some initial geological stress parameters in seepage-stress coupling damage behavior model. The new optimization method enhanced some computing strategies through combing with pattern search method and hierarchical optimization. The fact engineering example shows that the hierarchical pattern search method is high accuracy and validity in the cavern displacement parameter inversion of Qingjiang Shuibuya porject.7. Based on the finite difference software FLAC3D, the seepage-stress coupling damage behavior model procedure is designed. This procedure is proven by cavern displacement in Sichuan Qiaoqi hydropower project and used in Wuhan Fuhu mountain subway tunnel project.