Study On Stability And Non-linear Dynamic Character Of The Surrounding Rock System In The Deep-buried Tunnel

Along with the large-scale construction of infrastructures, such as South-to-North Water Transfer Project, Electronic Power Transmission from West to East, Qinghai-Tibet Railway, Transporting Natural Gas from West to East and West Traffic Infrastructure Construction, many long deep-buried tunnels and large underground engineering are inevitable. As the buried depth, span and length increase, so dose the groundwater osmotic pressure, geostress, and more nonlinear effect are manifested. But researches on these basic problems are still not solved. In order to reveal the mechanism of the failure of the deep-buried tunnel's surrounding rock and adapt to the development of the tunnel's designing and constructing, it is important to study the stability and nonlinear dynamic character of deep-buried tunnel's surrounding rock systematically.Funded 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 Chongqing Tongyu tunnel and Gonghe Tunnel as engineering examples, this paper focuses on the failure process of surrounding rock system in deep buried tunnel with traditional methods such as physical model test and numerical simulation and modern scientific tool such as nonlinear dynamics. And meanwhile, the coupling of stress-seepage fields was considered.From the research, the following conclusions were achieved:①The model material is made from powdery Fe3O4, powdery barite, quartz grit, epoxy resin, silicon rubber, gesso and so on, which density can range between 2.5～3.0 g/ cm3 with adjusting the content of powdery Fe3O4, powdery barite and quartz grit. And the tensile strength can range between 1.6KPa～24KPa, the cohesion can range between 1.2KPa～90.6KPa, with adjusting the ratio of epoxy resin, silicon rubber and gesso.②Both plain strain model test and three-dimension model test under high stress are carried out. The strain and crack extension of key parts is studied by applying full inner-spy photograph technology , the stress distribution character of key parts are analyzed by using of the strain measure technology.③Based on the rock sample uniaxial numerical tests, the stress character after peak value is studied. The relationship between soften character of rock sample after peak value and shear band is given, and the conclusion that the tensile breakage essence of rock sample under uniaxial compressing condition is caused by earlier shear damage is obtained.④According to the model material character, the Mohr-Coulomb criterion with tension cut-off strain- softening model is established and large-strain calculation method is adopted. The influence of high in-situ-stress on double-nonlinearity of surrounding rock mass is studied by contrasting result of physical model with numerical simulation on the base of physical model test.⑤Based on the orthogonal numerical experiment, the system stability is analyzed. Both the single-factor and multi-factor effect on some indexes such as tensile breakage volume, shear breakage volume, vertical displacement and horizontal displacement produced by some factors such as law of the of elasticity modulus, poisson ratio and soften modulus et al. are obtained.⑥Three-dimension hydraulic model of complex crack rock mass is obtained from research on crack fractal character of surrounding rock in deep buried tunnel and the FEM solution is put forward. SSOR-PCGG method is used and corresponding computer fortran program is given. It is proved that the model is effective and reasonable in application.⑦In order to study the unloading character of the surrounding rock system, the rock mass parameter is acquired by means of inversion method. Based on the simulation result, some nonlinear dynamics indexes(correlation dimension, largest Lyapunov exponents and Kolmogorov entropy) are calculated to study the evolution program of surrounding rock system quantitatively. It is found that the surrounding rock system is sensitive to initial conditions. The relationship between the surrounding rock system and external factor and that between surrounding rock system status and the energy dissipation are obtained.⑧By applying whole domain method,local region method to the engineering, contrasted, the predicting results of these displacement-predicting models agree well with the measured results; Aimed on the interaction of surrounding rock and support system, a nonlinear dynamic model is carried out. The nonlinear dynamic characteristics of surrounding rock and support system under high in situ stress is analyzed by reconstructing parameters in time series. It is proved that the dynamic model can predict the variation of the system characteristics parameters (axial force of anchor boat, surrounding rock displacement and radial stress of l support shot concrete ) very well and the study provided information for deep buried highway tunnel optimized design and construction. The research has good academic and practical significance...