A New Rock-Bolting Pattern Proposed for Tabas Fully Mechanized Mine Using Field Instrumentation and Numerical Modelling

The stability of longwall coal mines has been a challenging concern for geotechnical and mining engineers. Rock-bolting is the commonly used support system preventing roof and wall convergence and floor heave. This study attempts to suggest an optimized new rock-bolting pattern to effectively prevent the convergence of transportation and ventilation tunnels in Tabas coal longwall mine at panels 2 and 3. Three-dimensional numerical analysis was performed on the support system using FLAC^3d code. Investigating the rock bolts axial force applied to the ventilation tunnels roofs shows that, the safety factor of the new support system compared to the old one can be reduced by the ratio of 1.2 to 2, while the amount of the roof displacements are still within the allowable limit. Moreover, rock bolts installed in the transportation tunnels walls have yielded about 10 m from the working face, which became stable in the redesigned rock-bolting pattern. In order to decrease the floor heave, a support system with inclined bolts was proposed, in which the amount of floor heave in the transportation and ventilation tunnels decreased about 40% and 33%, respectively.