Mechanism and control of strong mine pressure in fully mechanized mining face of shendong mining area when crossing abandoned roadways in the same coal seam

In Shendong mining area, there may be several abandoned roadways ahead of some mining faces due to the adjustment of the face layout. In order to avoid roof accidents when the mining face crossing abandoned roadways, the occurrence conditions of mining faces and abandoned roadways, mine pressure control methods and effects in Shendong mining area were summarized, and the mechanism of roof advance fracture when the working face crossing abandoned roadways was analyzed. With the consideration of the different supporting effects of abandoned roadways, pumping pillars, coal pillars and supports, numerical simulation was used to study the subsidence and bending tensile stress of the main roof under different coal pillar sizes, roof periodic fracture positions, widths of the abandoned roadways, and strength of the pumping pillars. Results show that with the inclined angle between the roadways and the working faces decreases from 90° vertical to 0° parallel, the advancing length of the working face affected by the abandoned roadways decreases, where the effect intensity increases. The mine pressure of working face when crossing the abandoned roadways is mainly control by the size of the coal pillar, the position of the previous roof periodic fracture before crossing the abandoned roadways, the width and the supporting strength of the abandoned roadways. Due to the inevitable failure of the coal pillars with the mining face approaches the abandoned roadways, and the width of the abandoned roadways is difficult to change, the strengthen supports of the abandoned roadways and waiting mine pressure before crossing the abandoned roadways are always adopted to prevent main roof from advance fracture in Shendong mining area. With the peak strength and elastic modulus of the pumping pillars increase, the roof of the abandoned roadways will be supported better, but the pumping pillars may failure under great load caused by the overlong roof hanging. If the adjacent twice roof periodic fracture occur before and after crossing the abandoned roadways, the main roof can bear most of the overlying load during crossing the abandoned roadways and the mine pressure can be controlled effectively. Otherwise, the advance fracture of the main roof will occur as well as the roof caving and supports crushing. Finally, the fully mechanized mining faces of Halagou coal mine in Shendong mining area are taking as examples, and the mine pressure control effects of pumping pillars and waiting mine pressure during the process of crossing the abandoned roadways were analyzed, which can provid reference for the mine pressure control when crossing the abandoned roadways in Shendong mining area and even other mines. © 2024 China Coal Society. All rights reserved.