In order to enable safe pillarless mining in a deep, thick coal seam with a hard roof, an integrated approach combining presplitting roof blasting and a flexible formwork concrete support system was implemented and evaluated via theoretical analysis, numerical simulation, and field trials. The limit-equilibrium analysis indicated a minimum gob-side coal pillar width of approximately 6 m. A pumpable C40 flexible-formwork concrete was developed, achieving its design compressive strength within 28 days, to serve as a roadside support. Field implementation of the presplitting and composite support effectively controlled roadway deformation: total roof–floor convergence was limited to 340 mm (floor heave accounted for 65%), and support loads remained within safe ranges, with no structural failures observed. These results demonstrate that the proposed gob-side entry retaining technique maintains roadway stability without a coal pillar, offering a practical and economic solution for deep coal mines with hard roofs.
Ma et al. (Tue,) studied this question.