Research on the Deformation of Surrounding Rocks of Deeply Buried Hard Rock Tunnels with Different Incline

Research purposes: Because of the characteristics of stratification and structure form of deep buried hard rock bedding structure, the deformation and destruction of the tunneling surrounding rocks in such geological environment after loading have certain characteristics. This paper takes a high-speed railway Huangcao Tunnel as an example to carry out the numerical simulation analysis and evaluation on excavation damage and deformation of the surrounding rock of the hard rock combination along the deep buried tunnel under different dip angles, mainly studies the deformation of tunnel surrounding rock, yield progressive and stability of surrounding rock under the influence of different strata dip angle, and gives the failure modes of the surrounding rock of hard rock tunnel when the strength is reduced to the limit state. Research conclusions:(1) With the increase of strata dip angle, the main deformation of hard-rock composite bedding tunnel gradually changes from rock bending deformation to bedding sliding deformation. When the inclination angle increases to a certain degree (> 75°), the local displacement of vertical layer is relatively large, and the degree of bending deformation increases on the basis of mainly sliding deformation. (2) The excavation of the hard rock combination causes the surrounding rocks in a certain range around the cave to yield, and the change of rock inclination leads to the change of the yield area of the surrounding rocks. When the inclination angle is 30°, the yield range is the largest, which is used as the limit to decrease or increase the inclination angle. (3) There is a limit value of rock slope inclination, and the Huangcao tunnel in the hard rock combination is 40°, and the stability safety factor less than or greater than this value decreases, and the variation range of stability safety factor within the range of 10°~75° is up to 17%. (4) Under the condition of strength reduction, the failure mode of surrounding rock changes slightly, showing that: when the inclination angle is less than or equal to 30°, the displacement and failure range perpendicular to the bedding plane are large, and the failure mode of surrounding rock is dominated by stratification (bending fracture); When the inclination angle is greater than 30°, the failure range of the bedding plane is large, but the failure of the vertical plane starts first. (5) The research results have significant theoretical guiding significance and great engineering value for promoting the smooth construction of the high-speed railway and similar projects in the future. © 2020, Editorial Department of Journal of Railway Engineering Society. All right reserved.