Study on the Effect of Structural Joints on Tunnel Rockburst Mode

Under the action of structural stress, the internal joints of rock mass are generally developed, and the joints have an important effect on the occurrence of rockburst in deep tunnels. In order to study the relationship between the joints distribution and rockburst failure, based on the distribution law of rockbursts and structural joints in Caoguoshan tunnel, the distribution characteristics and evolution process of fractures are analyzed through acoustic emission data, and Rock Failure Process Analysis Software (RFPA) is used for research. The results show that the joints parallel to the tunnel axial direction are more likely to cause rockburst than those perpendicular to the tunnel axial direction. The joints hidden inside the surrounding rock and close to the excavation contour are more likely to cause rockbursts, while the change of their dip angle has little effect on the rockbursts. The existence of joint surfaces in the surrounding rock makes the stress rapidly concentrate in the thin rock mass between the joint surface and the excavation boundary, and the maximum principal stress will transition from the surface of the surrounding rock to the interior of the surrounding rock, and the stress boundary is in the shape of a concave arc, similar to the "V" or "pan" type blasting crater after rockburst. The research results have certain reference value for the planning and route selection, rockburst prediction and prevention of actual projects.