Discrete Element Analysis Of The Dimension Design Of The Protective Coal Pillar Under The Segmental Structure Of An Inclined Shaft

:At present, coal pillar is an effective method to protect the roadway in mining engineer and widely used at home and abroad. However, it is difficult to recycle the coal pillar, which will induce waste of resources. Therefore, explore the width of coal pillar has a universal economic and social significance, for it is not only conducive to the stability and safety of the roadway, also improve the recovery rate of coal resource as far as possibleThe inclined shaft of Xin Jie coal mine is constructed by TBM method. Based on the problem of designing coal seams mining in Xin Jie coal mine, this paper aims to determine the reasonable size of the coal pillar by analyzing the characteristics of the inclined shaft’s internal force and displacement in the process of exploiting coal and mine. While the existing empirical methods only involves the lumped geometric and mechanical properties of the coal seams, numerical simulation methods can simultaneously take into account of the geometric and mechanical characteristics of the rock layers, the structures of the inclined shafts as well as the coal seams.This paper uses the method of discrete element numerical simulation, whose main research contents and achievements are as follows:(1) Presuppose several widths of coal pillars in the3-1coal seam and simulate the mining processes from the distant to the near through selecting sections at different locations of the inclined shaft with UDEC software. Analyze stress and deflection of the inclined shaft’s structure depending on coal pillars with different widths, and regard the minimum width of coal pillar making the inclined shaft structure meet the requirements of safety and stability as the suggestion. In the process, the less horizontal distance between the mining working surface and the inclined shaft, the more disadvantageous to stress state of inclined shaft and the larger displacement is. Similarly, the more vertical distance between the seam and the inclined shaft, the more advantageous to stress state of inclined shaft’s structure, but the lager displacement is. At the same time, UDEC software can directly simulate and get the slip region of the joints, and get the rock rupture angle which is76degree.(2) Based on the2-D simulation, the angle between the seam working surface and inclined shaft’s axis in the horizontal plane is calculated as1.53degree, which taking into account the angle of the inclined shaft6degree. And performed it in the width of a working face at the bottom of the inclined shaft by3-D stimulation. The simulation results show that, firstly, it is benefit to the safety and stability of the inclined shaft structure if the working surface of mining is nearly parallel to the axis of inclined shaft. And secondly, the widths of coal pillars in different seams mining in order from the upper one to the lower can greatly influence each other. For example, if the width of the upper seam (3-1) is40meters, the lower seam (5-1) needs at least86meters; and if3-1seam is50meters,5-1seam only needs67meters.(3) Taking the solid3-D model as basis, this thesis makes contrast analyses between the stimulated results of full coupling method when fluid is flowing in fractures and results of three-dimensional solid mechanics. It draws the conclusion that the existence of fluid is against the stress of inclined shaft structure and contributes to a smaller displacement contrasting to a non-fluid situation, meanwhile, increasingly uneven displacement replacing the stress of inclined shaft becomes the control condition of coal collars’width.