Optimization Support Controlling Large Deformation of Tunnel in Deep Mine based on Discontinuous Deformation Analysis

Field investigation and numerical analysis both show that the effects of multi-dynamic pressure on the tunnel deformation and failure in Qianjiaying coal mine are the main reasons, namely, the dynamic pressure of mining adjacent coal seams, the dynamic pressure due to the effects of mining the upper coal seams on the down coal seams and the advance dynamic pressure of coal seam. Field data indicate that the horizontal displacement is more than vertical displacement, which mainly due to the horizontal stress greater than the vertical stress. Through discontinuous deformation analysis (DDA), we have analyzed the shortage of the old support design, and put forward the revised support design. The functions of three adopted cables are different, namely, the middle cable is used to control the displacement of roof strata, and both sides cable are used to transfer the stress of the overlying strata. The corner bolts are used to control the squeezing pressure of two sides of tunnel, so as to effectively control the floor heave of tunnel. Based on DDA analysis, the failure process, deformation field, stress field and damage scope of tunnel under different support design have been investigated. Results have indicated that the DDA method is the potential method to optimize the bolting support design for coal tunnel.