Synergistic reinforcement using pressure releasing and energy absorbing method under hard roof: Physical model test

During fully mechanized caving mining of thick coal seams, a large amount of strain energy accumulates in the roof, especially when the roof is thick and hard, making it difficult for the roof to collapse naturally. When the roof eventually collapses, the accumulated energy is released instantaneously, exerting a strong impact on the roadway. To address this issue, we proposed the synergistic control method of directional comprehensive pressure relief and energy-absorbing support (PREA) for roadways with hard roofs. In this study, we developed a three-dimensional physical model test apparatus for roof cutting and pressure relief. The 122108 ventilation roadway at the Caojiatan Coal Mine, which has a thick and hard roof, was taken as the engineering example. We analyzed the evolution patterns of stress and displacement in both the stope and the roadway surrounding rocks under different schemes. The PREA reinforcement mechanism for the roadway was investigated through comparative model tests between the new and original methods. The results showed that, compared to the original method, the new method reduced surrounding rock stress by up to 60.4%, and the roadway convergence decreased by up to 52.1%. Based on these results, we proposed corresponding engineering recommendations, which can guide field reinforcement design and application. The results demonstrate that the PREA method effectively reduces stress and ensures the safety and stability of the roadway.