Investigating the effect of simultaneous extraction of two longwall panels on a maingate gateroad stability using numerical modeling

In longwall mining method, the stability of the maingate and tailgate gateroads is of great importance because these excavations are used for essential services such as ventilation and transportation. The aim of this paper is to develop a numerical model to investigate the stability of a maingate gateroad named P8-maingate during caving and extraction of P7 and P8 coal panels of Tabas Parvadeh underground mine. Stability analysis is carried out by critical shear strain criterion, zone plasticity conditions, support system efficiency and strength-stress ratio conditions using FLAC(3D), a software based on finite difference numerical methods. In the critical shear strain criterion method, the stability analysis is conducted by comparing the shear strain increments of the element in the model and Sakurai critical shear strain. In the second stability analysis method based on zone plasticity, the zones indicating shear plastic failures are the potential instability-causing regions. In the support system efficiency method, the applied load and pressure are compared to the yielding strength of the support systems to check their stability. In the Strength-Stress Ratio (SSR) method, a safety factor is determined for the gates, and the strength versus stress plots of the gates are assessed to control the stability condition. The results of numerical modeling indicate the stability of the P8-maingate using these methods. The modeling results are then compared to the instrumentation data to investigate the consistency where a good agreement was observed.