In Longwall mining, gateroads play a major role in transporting men and materials and providing ventilation. Barrier pillars lie between two adjacent panels to support the face and gateroads. During the retreating, these gateroads and barrier pillars are subject to mining-induced stresses and may cause the failure of the face, barrier, roof and floor of gateroads. The behaviour of barrier and face must be assessed to extract the panel successfully. For this, a longwall panel of 250 m x 2500 m size lying at 530 m depth is analysed using 3D finite element modelling technique. This study considers the variations in retreat distance, coal properties, and barrier size. All the numerical models are analysed considering Mohr-Coulomb criterion. The vertical displacement in gateroads and stress on the barrier and longwall face, abutment zone and yield zone are analysed, and the safety factor of the barrier pillars and longwall face are determined.
The longwall mining is proven as the most suitable technique to extract the coal from deep underground mines with safety. The barrier pillars and gateroads that are driven into virgin coal to develop the longwall panels and are required to stand and support the coal excavation operations until the panel is mined. During the retreating, stress develops on the barrier pillars, working face, and neighbouring panels, convergence occurs in the roof and heaving observes in the floor of gateroads and face. As a result, the barrier pillars, face, and gateroads may deteriorate, and lose their stability and may start to yield (Colwell et al., 2003; and G. S. Esterhuizen et al., 2019).
The behaviour of the barrier pillars and gateroads must be required to determine the optimum size of the barrier to extract the coal from deep longwall panel safely and effectively. Several investigations on the behaviour of the barrier pillars, longwall face, and gateroads have been carried out based on theoretical, empirical, and numerical approaches. Most of the study have been conducted by collecting real field data from the mine site (Gearhart et al., 2017; Tulu et al., 2018; and G.Esterhuizen et al., 2019). Shi et al., 2021 conducted the study to determine the roof convergence, stress and abutment zone in the longwall face.
