| As an important integrated coal and coal power production base in East China,Huainan mine is of great significance to the regional economic development.The safety of the working face is threatened by the local direct overburden of thick hard tops in Group A coal in Huainan mine,therefore,it is crucial to investigate the breaking and collapse law of the direct overburden of thick hard tops and the bearing performance of the hydraulic support in the mining site.In this paper,the collapse characteristics of the working face under direct overburden of thick hard roof are studied by using theoretical mechanical analysis,numerical software simulation,physical similarity simulation and on-site engineering practice monitoring,and the mechanical model of the roof under different support conditions is constructed.The thesis also discussed the effect of pre-cracking and roof cutting on the control of mine pressure at the working face,determined the reasonable pre-cracking and blasting roof cutting technology scheme under the action of mining,and carried out the application of pre-cracking and blasting roof cutting engineering.The main research work of this thesis is as follows.By analyzing the transport law of the straight overlying thick hard basic roof during coal seam recovery,it is found that the thick hard roof is not easy to collapse independently due to its own strong lithology,thus it is easy to form a long cantilever structure roof,under the action of self-weight and overlying load,the thick hard basic roof gradually bends,and then suddenly breaks and sinks,releasing a large amount of energy,causing the phenomenon of overloading the working face bracket or even crushing the hydraulic bracket strong dynamic load.Based on the key layer discriminant theory,it is determined that the directly overlapping thick hard top is the key layer of bearing.Based on the theory of plate structure,the support condition of the top plate was changed from "four sides solid support" to "three sides solid support and one side free" during the recovery process of the first mining face,and the deflection surface equation of the plate structure was initially determined,and then combined with the theory of plate structure,it was deduced that the initial After that,the sensitivity of the influencing factors of the initial breakage and the periodic breakage of the directly overlapped thick hard top plate was analyzed as a control variable,and it was revealed that shortening the breakage step of the directly overlapped thick hard top plate could reduce the incoming compression strength of the thick hard top plate.According to this preliminary calculation,ZZ13000/24/50 type support cover hydraulic bracket was selected as the mining support equipment.According to the "step collapse" model,the interaction model between brace bearing and roof breaking body is established,and the reasonable range of roof cutting step that can be adapted to the brace in the quarry is determined.Using 3DEC and UDEC numerical simulation software,the simulation results of overburden collapse characteristics,stress changes and brace resistance at different roof cutting steps of15 m,20m and 25 m were compared and analyzed,and it was found that a small roof cutting step is more conducive to mine pressure control at the working face.After pre-cracking and roof cutting,the mining fissures and mining stresses in the working face were studied,and the trend of overburden fissure development was obtained.After pre-cracking and roof cutting,the prefabricated fractures cut off the path of stress propagation in the rock stratum,forming a "pressure relief zone" in both this working face and the overburden working face,which has a certain control effect on the intense mine pressure of the coal rock body.Combined with the construction of deep hole pre-cracking blasting roof cutting and observation of site data,the working face top pressure characteristics,including hydraulic support resistance and pressure step data analysis.The comprehensive data pointed out that the selected quarry bracket with over-advance pre-cracking blasting roof cutting can meet the working face roof control requirements during normal mining of coal seam.Figure 57 Table 13 Reference 89... |
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