Study on deformation and failure characteristics of jointed surrounding rock using a physical model composed by interlooking blocks

During the construction process of blocky rock mass tunnels, the phenomenon of falling arch blocks frequently occurs. To truly reflect the deformation characteristics of the surrounding rock, an interlocking structure block model method considering the distribution characteristics of the surrounding rock structural planes was proposed, and the rationality of the structured block model was validated through numerical calculations. First, by conducting an interlocking structured block model test, the deformation and failure characteristics of the tunnel section during the excavation process were analyzed, and the displacement of the surrounding rock clearly exhibited asymmetrical deformation. Owing to the interlocking effect of nonpenetrating blocks, the torsion and subsequent gyration of the blocks limited the range of surface damage to the surrounding rock, ultimately resulting in shear fracture during the overload test. Second, compared with the phenomenon of small deformation of the surrounding rock in the continuous medium model, whose bearing capacity is 9 times that of geostress, the nonpenetrating structural plane inlaying structure block model formed a pressure arch structure with a height of one quarter of the tunnel diameter, resulting in a bearing capacity that is twice as high as the geostress, which is closer to the actual engineering situation. In addition, the prestressed rock bolt support technology effectively controlled the deformation of the surrounding rock of the block test model, and the deformation of the surrounding rock was controlled at 6.5 mm through field testing. The block test model accurately reflects the variation characteristics of jointed surrounding rock and provides a reference for tunnel support design.