Experimental study on the deformation and failure mode of surrounding rocks of a tunnel in a jointed rock mass

• Published in: Engineering failure analysis 2024-09, Vol.163, p.108470, Article 108470
• Main Authors: Sun, Bing-jun, Mei, Yu-chun, Li, Wei-teng, Zhang, Chang-an, Shao, Xing, Li, Ting-chun, Li, Wen-xu, Zhao, Wen-xin, Wang, Lu-ping
• Format: Article
• Language: English
• Subjects: Jointed rock mass; Model test; Numerical simulation; Prestressed rock bolt support; Rock bolt failure; Surrounding rock control; Tunnel instability
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2024.108470

•The deformation instability process and critical load of jointed surrounding rock are analyzed.•The interaction mechanism between prestressed rock bolt and jointed surrounding rock is studied.•The feasibility of prestressed rock bolt controlling the deformation of jointed surrounding rock is verified. The existence of jointed rock masses in tunnels is a key problem that leads to the deformation and instability of the surrounding rock. Based on the engineering background of the Qingdao Metro, a physical model and a numerical model are constructed to analyze the mechanism of deformation and instability of the surrounding rock of a jointed tunnel using model blocks that conform to the characteristics of joint distribution. The results show that during the whole test process, the cracks between the blocks in the tunnel arch are in the “development − stability − closure − penetration” state. Finally, the block falls in the left area of the tunnel, and the corresponding anchor axial force transits from the linear growth stage to the steady growth stage. After the axial force of the rock bolt suddenly decreases in the loading stage, the bolt enters the stability stage, and finally, S-shaped failure occurs when the surrounding rock is unstable. Under the action of a prestressed rock bolt, the normal stress and radial stress of the rock mass increase, and the difference between the major and minor principal stresses decreases significantly. The radial stress on the surrounding rock surface of the arch is approximately 8 % greater than that in the traditional rock bolt scheme, which improves the strength reserve of the rock mass. In the field test, the prestressed rock bolt can control the deformation of the surrounding rock in the arch within 2 ∼ 5 mm, which provides a reference for the control of the surrounding rock in jointed tunnels.