Research On Stability Of Thin Lofty Broken Roof In Large Cutting Height Workface And On Control Technology

Due to the tense situation of coal resources in Huainan Panxie Mining Area, it is of an important significance to study the exploration of Coal Group named A. According to the geological conditions of11223working face in Pan Two coal mine, this paper analyzed the caving mechanics mechanism and reinforcement mechanism of broken roof in theoretically, then discussed the thin soft broken roof stability in this working face with large mining height and control technology combining of numerical simulation and field measurement.A three-dimensional numerical model was established by FLAC3D numerical simulation software, on this basis, adopted numerical simulation method with different mining thickness and different mining width, to comparatively analyze the distribution characteristics of overburden stress and the stress characteristics in the thin soft broken roof. At the same time, a comparative analysis of roof convergence and distribution law of abutment pressure was build, the results showed that:(1) Under different mining heights, the position of stress peak value in front of the coal wall and the one in the coal pillar but behind the cutting hole is proportional to a certain heights, however, the influence range of mining is not proved to be relate to the heights;(2) Also under different mining heights, the shape of stress arch in goaf develops from flat type to saddle type with the increase of the length of the working face, and the expansion change and the range of stress arch in front of the coal wall or behind the coal pillar is basically the same;(3) The stress peak value in the coal pillar but behind the cutting hole along the strike of working face and the maximum relative stress concentration coefficient are nonlinear proportional to the length of the working face, in addition, the relationship between the length of the working face and the stress peak value in front of coal wall along the strike of working face and the maximum relative stress concentration coefficient is similar;(4) The roof subsidence at the rear of the working face gradually increased with the increase of distance from coal wall, finally trend to be stable. According to the 6observation, the maximum roof subsidence is345mm without grouting, but169mm when grouting, the date forms the obvious differences, which can be inferred that grouting plays a significant role in the control to the roof subsidence;(5) The maximum lead abutment pressure in front of the working face which is not grouted is33MPa, and the peak value of advance stress concentration coefficient is3, in comparison, the one in the non-grouted area is30MPa,and the concentration coefficient is2.75,it is not hard to found that the maximum lead abutment pressure decreases by9.3%, and the concentration coefficient also reduces obviously, thus can be concluded that the roof integrity is enhanced after grouting, the influence degree of advance stress to the non-grouted area in the roof is much smaller than the one in the grouted.In conclusion, The research results can provide a theoretical reference for the site, which is also guiding significant to the mining security with the condition of high thin soft broken roof in Huainan Panxie Mining Area.