Stability And Instability Process Analysis Of Steep Coal Seam Of No.104 Group In Xinjiang

With the rapid development of urban construction and economy in China,urban construction expands rapidly to the surrounding areas.In the construction process of some mining cities,many construction projects inevitably encounter the adverse geological conditions of the goaf of coal mined out,if they are not treated,these land resources will be put wasted,hindering the development of the city.The stability evaluation of the coal mined out area is an important work before the construction project is carried out in the goaf area.In this paper,the exploration and treatment project of 104 group coal mined out area in Urumqi,after detailed investigation of the mining area,the stability and instability process of the goaf are analyzed in depth by combining theory with numerical simulation methods,and the following results are obtained:(1)Combined with the methods of field investigation,geophysical exploration,drilling and theoretical calculation,the occurrence characteristics of goaf and the spatial and temporal distribution characteristics of surface subsidence in the study area are described;the stability of goaf in steep coal seam in the study area is calculated and evaluated,and the evaluation results show that the goaf in each coal seam in the study area is unstable.(2)In this paper,PFCZD discrete element particle flow program analysis method is used to simulate and analyze the process of stress change and roof deformation of goaf pillars in the process of mining inner steep coal seam.It is concluded that the mechanism of goaf instability in the study area is the chain reaction of goaf group instability caused by failure and fracture of goaf roof in B7 coal seam.(3)In the underground mining of steep and close seam group,the surface subsidence deformation shows the asymmetric and abrupt subsidence basin,and the profile shows the asymmetric "W" distribution.After the mining of B7 coal seam,the abrupt change of the maximum subsidence value of the surface subsidence basin in the goaf is particularly obvious.The maximum subsidence value of the surface at the monitoring point reaches-6.995m,and there are subsidence pits on the surface.After the B6 coal seam is mined out,the distribution of the maximum subsidence value in the mined out area of B7 and B6 coal seams reaches-25.346m and-24.934m.(4)According to the analysis of the instability process of goaf under the influence of different factors,the following three conclusions are drawn:? In view of the instability process of goaf in steep coal seam under the influence of different mining methods,five numerical calculation models of different mining methods under different geometric factors are established.It is concluded that the stability of goaf in steep coal seam is directly proportional to the width of coal pillar under the same mining height and different width of coal pillar,and the stability of goaf in steep coal seam under the same width and different mining height It is inversely proportional to the mining height;?The analysis of the instability process of goaf under the influence of time shows that after the end of mining activities,with the passage of time,the whole process from dynamic deformation and displacement to the final stable deformation and movement of goaf is completed.The dynamic deformation and movement process are mainly the bending deformation of the rock column and the collapse of the surface loose layer into the goaf.The static deformation and movement of the final stable state are mainly the deformation and movement process of the residual void in the goaf under the external factors.?According to the analysis of the instability process of goaf under the influence of earthquake,the EW and UD directions of Wolong wave monitored by Sichuan earthquake are used for research.The results show that after the earthquake,there are two big cracks on the top of the roof rock pillar in the mined out area of b 11-12 coal seam exposed inside and on the surface,and the deformation subsidence value reached-5.331m.With the passage of time,the roof pillars may collapse and cause secondary disasters.