Study on Disaster Mechanism of Roadway Deformation and Roof Energy Accumulation in Advance Working Face

Abstract

It is one of the important disasters faced by coal mine that roof energy accumulation leads to its advance failure and roadway failure. Identifying the position of roof energy accumulation can predict the position of roof advance failure and roadway deformation, so as to take preventive measures. Based on two generalized displacement beams, the accumulation law of the bending moment and energy density of the top coal wall under different loads, different thicknesses, and different cantilever lengths is investigated. The following conclusions are drawn: (1) Under different load conditions, the peak of the bending moment and energy density both appear at 10 m in front of the coal wall and rapidly decrease to 0 after reaching the peak and no longer change. The peak value of the bending moment increases linearly with the increase of the load, and the relation is M = −143.32q − 286.63. The peak value of bending moment changes exponentially with the increase of load, and the relation is U^e = 200.46e^0.42q. (2) Under different thicknesses, the bending moment of the thickness to the rock layer has an irregular distribution at the peak value. When the thickness is 12.5 and 15 m, the change tends to be consistent, and when the thickness is 7.5 and 10 m, the bending moment of the roof is small when the thickness is 17.5 m. When the thickness is less than 17.5 m, the smaller the thickness is, the larger the peak value is, and the more advanced the peak value is. The smaller the thickness of the roof, the smaller the range of energy density accumulation. (3) Under different cantilever lengths, with the increase of cantilever length, the peak bending moment presents a linear increase, and the relationship is M^e = −158.22 L + 137.4, and the range of bending moment accumulation increases with the increase of the roof cantilever length. With the increase of the cantilever length, the peak energy density of the roof increases exponentially, and the relationship is U^e = 3.5536e^1.1067L, and the lead energy accumulation distance of the roof increases. (4) When the thickness of the roof is 10 m, the stress peak occurs more frequently within 5–15 m in front of the working face, which well confirms the correctness of the theoretical analysis.