The Influence of Different Influencing Factors in the Jointed Rock Formation on the Failure Mode of the Tunnel

The jointed surrounding rock is a geological condition that is frequently encountered during the construction of tunnels. The deformation and strength of jointed rock masses have an obvious anisotropy, and these mechanical properties could easily contribute to a number of factors, such as large deformation, collapse, initial support damage, and secondary lining cracking, during the construction process. Therefore, in this paper, the failure mode of the jointed rock is investigated, and the relationship between factors such as the dip angle of the joint, the joint spacing, the cover depth of the tunnel, and the stability of the jointed surrounding rock is explored with the help of the Shengli Tunnel. The results show that: (1) As the joint dip angle increases, the failure mode of the surrounding rock gradually evolves from flexural failure to shear-slip failure. (2) When the jointed spacing is between 0.5 and 2.0 m, the surrounding rock shows obvious anisotropy. As soon as it is greater than 2.0 m, the deformation of the surrounding rock decreases and the stability of the surrounding rock will be improved. (3) The increase in the surrounding rock stress caused by the cover depth could result in a more significant unsymmetrical loading phenomenon. The yield area is primarily focused on the left arch shoulder and right arch foot, which should be supported and monitored during the excavation.