Comparative Analysis of Two Kinds of Support Structure in Jointed Rock Tunnels: Rock Bolts and Steel Arches

Rock bolts and steel arches are common methods of support used in tunnel engineering. To compare the support efficiency of rock bolts and steel arches, numerical simulations were conducted using discrete element software to analyze the mechanical response characteristics and tunnel stability of support systems. Firstly, the supporting effects of rock bolt and steel arch supports were studied, taking into consideration the different buried depths of the tunnels. The combined effect of rock bolt and steel arch supports under different parameters was also studied. The results show that, at a burial depth of 17 m, both support methods have similar surrounding rock deformation reduction ratios. When the depth is less than 17 m, steel arch support reduces deformation better than rock bolts; when it exceeds 17 m, rock bolts outperform steel arches. In addition, the prestress value and length of rock bolts were shown to be negatively correlated with surrounding rock deformation. As the prestress value rose, roof settlement decreased by 46% and stayed constant when it exceeded 120 kN. As the bolt length increased, roof settlement decreased by 39% and remained unchanged after reaching 3.5 m. In joint model tests, the prestressed rock bolt was found to inhibit the deformation and failure of the surrounding rock. The optimized support parameters were applied to the engineering field, and field verification revealed that the settlement of the tunnel vault was stable at 4.8 mm after 40 days, which effectively controls the deformation of the tunnel. The research results provide a reference for the selection and design of surrounding rock support methods for tunnels.