Study On Instability Mechanism And Control Technology For Coal Wall Of Large Mining Hight Fully-Mechanized Mining Working Face Of Coal Seam 3# In Lu’an Group

Thickness seam and medium-thickness seam of coal resources is of wide distribution and the large proportion in the occurrence and exploitation,so its rational mining is of extraordinary significance the overall level of science and technology research in Chinese coal industry and economic contribution capacity.In recent years,as for large mining height full-seam fully-mechanized mining,because it has the advantages of a high rate of mining resources,mining of coal dust in the face in low gas emission less,roadway layout is simple,safe and efficient and other aspects,it has received the attention of the majority of experts and scholars at home and abroad,and has made a large number of scientific research on the stability and control of coal mining field,and now the technology has been widely used in below 6.5m thickness coal seam mining.But the research of mine pressure behavior law and surrounding rock deformation control for above 6.5m large mining height full-seam fully-mechanized mining still be seldom.In this paper,we take it for an example of Lu’an Group Wangzhuang Colliery 8101 large mining height full-seam fully-mechanized mining(maximum mining height 6.8m)project,and through theoretical research,computer simulation software,project monitoring and other methods of large mining height full-seam fully-mechanized mining working face stability control conducted the following research:(1)Through the on-site project field measurement,the engineering geological information of coal seam occurrence conditions,fracture of surrounding rock structure,crustal stress,characteristic of strata behavior,rib spalling form,rib spalling coal body size and shape for Wangzhuang colliery large mining height full-seam fully-mechanized mining working face were gotten.(2)Through the theoretical research,we analyzed the reason of rib spalling instability,and concluded that the rib spalling of Lu’an Group Wangzhuang Colliery 8101 large mining height full-seam fully-mechanized mining working face is due to the surrounding rock of coal quality’s relatively soft,and rib spalling arise from coal body shear failure.While the large mining height appeared vigorous,abutment pressure peak and larger scope,large stress concentration coefficient and other factors,resulting in a large coal-high wall shear stress area coverage,severely coal wall shear failure,rib spalling occurred frequently,and the unprecedented large of scale rib spalling.(3)According to the consequence of rib spalling situation observed statistical results for Lu’an Group Wangzhuang Colliery 8101 large mining height full-seam fully-mechanized mining working face,and combining with relevant references,we proposed and established a "circular conical surface wedge-shape" rib spalling structural model and derived their destructive instability judgment criterion.(4)On the basis of analyzing and summarizing the existing results and contrasting by all kinds of existing achievements’advantages and disadvantages,we proposed a new scheme which use staircase coal wall to control rib spalling,and made a qualitative analysis of its mechanism of action.(5)We carried on the computer simulation analysis by using software FLAC3D and concluded as follows:to improve working resistance of support for the coal wall stress,plastic zone distribution has little effect;grouting coal distribution on the stress and plastic zone coal wall bracket slightly higher than increased support work load;to accelerate velocity distribution on the working face has more obvious affect on the distribution of coal wall stress and plastic zone;to reduce the cutting height has more obvious affect on distribution of coal wall stress and plastic zone;Staircase Coal Wall has the most large affect on the distribution of coal wall stress and plastic zone,since changing the shape of the coal wall,coal wall plastic area is also significantly reduced.In combination with the actual situation of technical conditions,and comprehensive comparison groups simulation results,we obtained that using the upper and lower levels of fault coal wall horizontal dip separation of 1.2m,a height ratio of 9:7(3.7125m:2.8875m),2-grade staircase coal wall is the best option.(6)As for this article referred to Staircase Coal Wall the monitoring results Lu’an Group Wangzhuang Colliery 8101 working face industrial test case analysis shows:switching on the lower level of fault coal wall horizontal dip separation of 1.2m,height ratio of 3.5m:3.1m 2-stage coal wall propulsion working face,the number,depth,width and height of coal wall rib spalling are significantly reduced,essentially to ensure safety in production on large mining height face,and verified the referred Staircase Coal Wall has significant control effect on large mining height full-seam fully-mechanized mining working face rib spalling instability,and provides some engineering experience for large mining height full-seam fully-mechanized mining working face rib spalling governance.