Model Test And Theoretical Analysis Of The Interaction Of The Surrounding Rock And Supporting System Of Underground Engineering

Along with more and more long-large-deep tunnel appears, even tunnel group, its stability is becoming the key problem for the design and construction. But researches on the failure mechanism of surrounding rock are still not matured owing to complex and uncertain geology in tunnel, and the current study, thinking little of the failure process and the interaction of the surrounding and the bolt.Founded by"research on the stability and reliability of tunnel and underground space structure"(a key project of National Nature Science Foundation of China)and taken Gonghe Tunnel(which was located between the villages and towns of Wulong and Pengshui, one segment of interprovincial highway from Chongqing municipality to Changsha metropolis) as engineering examples, this paper focuses on the failure process and the variation of the stress of surrounding rock system in deep buried tunnel and the variation of the axial force of the bolt with physical model test and numerical simulation. From the research, the following conclusions were achieved.(1)The model material is made from epoxy resin, polyamide, silicon rubber, firming agent of silicon rubber, quartz grit, powdery barite and gasoline. The model material has steady performance and has a good repeatability. For using gasoline as solvent, it can be dried quickly. The measured values of the main physical and mechanical index of the model material is closed to the theoretical values, so the model material adapts to simulating rock-mass.(2)According to rock character of a certain soft rock tunnel, the physical model test of the tunnel is made in the triaxial model-test machine. The whole failure process was observed by applying full inner-spy photograph technology, with it the deformation and crack extension of key parts is studied. By using of the strain measure technology, the strain of key parts of the surrounding rock and the bolt are measured, according to this, the variability of the stress of surrounding rock and the variability of the axial force of the bolt are studied.(3)Based on the mechanical property of the model material, the Mohr-Coulomb criterion with tension cut-off strain-softening model is established The numerical simulation of different conditions are worked with the same boundary condition as the model test, according to this, the plastic zone, stress field and the deformation of the surrounding rock are studied, the variation of the axial force of the bolt is studied. The calculation results of different conditions are compared.(4)The variation of stress of the surrounding rock of the model test are compared with the numerical simulation.(5)The strain increment is regarded as a criterion to estimate the stability of the surrounding rock of the numerical simulation. We compare the failure process of the model test with the numerical simulation and draw the conclusion that the two processes coincide with each other.(6)Aboved on the result of the overloading model test, a definition of safety factor is given. According to this, we give the safety factor of different conditions.