Study On Surrounding Soft Rock Stability Of Tunnel In High Stress

The technique development and the safety production of coal mine have been restricted by the problem of soft rock in high stress in many coal mines, and it has a great theory and practical importance to study on the stability of soft rock tunnel in high stress and the combined supporting technique.The bolt-net-anchor-spray coupling support theory which adapts to the surrounding soft rock deformation control of tunnnel in high stress is discussed based on massive referencing articles, and we can abtained that the surrounding rock is in the best self-stability state when the section configuration is completely coupled with natural stress by using the tool of FLAC3D, and it's the best method to make full use of self-stability of surrounding rock through employing the coupling of section configuration with natural stress. In practical tunnel design, the section configuration can't be fully coupled with natural stress, so the direction of longer radius of the tunnel should be along the direction of maximum principle stress as possible as it can, and then the bolt-net-anchor-spray coupling support in critical parts is adopted for compensation.The basic principle of self hidden arc theory and its application in high stress soft rock are discussed in the paper, and the formation process of self hidden arc is simulated by using FLAC software and the design basis of the bolt-achor is generalized too. At the same time, base on the engineering background of Jin Hua Shan Coal Mine, the shape and size of cross-section and the supporting parametre are designed optimizedly through in-situ observation and sampling to improve the deficiency of original support, and the three-dimensional numerical model of Jin Hua Shan high stress soft rock tunnel is established by adopting the FLAC3D software. FISH program is used to control the digging, the footage is 0.8m in one step, and the 24m long test part can be finished in 30 steps. When the digging is finished first and then the bolt is constructed, the time difference between them in one step can realized by adapting the stress-free method. The variation of stressed bolt in the process of tunnel digging, the digging affection to the deformation of surrounding rock, and the tunnel digging affection to the initial test part surrounding rock are simulated, respectively.The simulating results indicate that the optimized design scheme is well and the rationality of this optimized design is examined. The regularity of bolt stress which varying with digging process of tunnel is obtained through numerical simulation, and the reason that the sides of tunnel and deeper parts of bolts are mainly in compression state at the beginning of the digging is explained. The deformation failure mechanism of high stress soft rock has been got through numerical simulation of surrounding rock deformation in digging and the understanding of variation of the displacement and stress of supported rock with digging process. The reason that the deformation is rather obvious at the start of the test and its varying regularity are proved, and the numerical simulation analysis is done for existing supporting design, and obtained a significant conclusion for subsequent supporting test, which improves the supporting conditions of Jin Hua Shan Coal Mine and provides a powerful protection for safe-fast production of the mine.