Simulation Study on Spatial Form of the Suspended Roof Structure of Working Face in Shallow Coal Seam

Longwall fully comprehensive mechanized mining is mainly used for the working faces of shallow coal seam with large mining height, which usually have a large suspended roof at the face end. The overhang at the face end leads to stress concentration, which affects the safe mining of the working face. In this paper, we use the 15210 working face with a suspended roof (overhanging area 50 similar to 70 m(2)) of the Zhangjiamao coal mine as study background, with physical simulation, numerical calculation and theoretical analysis, the spatial morphologies and changes in the roof structure at the face ends of the working face in shallow coal seam are obtained, in which the suspended roof increase from the bottom to top, forming step-laminated structures. The caving interval of the suspended roof at the face end is about two times the period weighting interval, and the suspended roof area at the tailgate is smaller than at the headgate. The distribution of the shear and the principal stress field at the face-end region is arc-shaped, and the distribution of the plastic zone shows that the collapse of a suspended ceiling has obvious hysteresis. According to the simplified analysis of the Marcus plate, when the layers of the stepped curved triangular plates increase, the length of the suspended roof on the solid coal side also increases, which is consistent with the results of the physical simulation and numerical calculations. The formation mechanism of the roof at the end of the working face provides a research foundation for the control of roofs found at face ends and further improves the theory of roof structure and the safety mining of suspended roof areas.