| With the improvement of coal mining technology and the continuous development of mining equipment,China’s coal production capacity has been increasing,and a number of 10 million ton mines have emerged.However,with the increase in production capacity,the intensity of coal mining is also increasing,often causing strong mine pressure to appear in the roadway,increasing production costs and threatening mine safety.Strong mine pressure manifestation is an intense dynamic disaster phenomenon in which the energy gathered in the coal rock body is released slowly or instantaneously in a larger amount,and the coal rock body is damaged,while a large amount of energy is released.In this thesis,the header working face of the double-system extra-thick coal seam mine in China is taken as the research object,and the research on the laws and control techniques related to the strong mine pressure manifestation in the header return tunnel of the extra-thick coal seam mine is carried out through theoretical,numerical tests and field measurements.The strong mine pressure phenomenon at the working face of the lower coal seam in the downstream mining process of Xiaojiawa coal mine is analyzed to clarify the engineering problem of strong mine pressure;the influencing factors triggering the appearance of strong mine pressure in the comprehensive mining of extra-thick coal seam are analyzed and the law of its action is studied;the mechanism of the appearance of strong mine pressure in the comprehensive mining of extra-thick coal seam is studied;finally,the technical measures for the prevention and control of strong mine pressure in the comprehensive mining return roadway of extra-thick coal seam are determined to provide a theoretical basis for safe and efficient mining in coal mines under similar engineering geological conditions.The main research results of this paper are as follows.The main research results of this paper are as follows:(1)This paper analyzes the phenomenon of strong rock pressure in the working face of the lower coal seam during the downward mining of Xiaojiawa Coal Mine,and clarifies the engineering problem of strong rock pressure in Xiaojiawa Coal Mine.The strata distribution characteristics of the "Carboniferous-Permian" double system coal seam mining are analyzed,and the evolution law of the vertical stress field in the strata between the two coal seams during the downward mining process of the "Carboniferous-Permian" double system coal seam is obtained.This paper reveals the driving mechanism of strong rock pressure stress under the two alternative modes of "skip mining between mining areas" and "sequential mining within mining areas" in the process of mining extra-thick coal seams.Compared with the replacement method of "sequential mining in the mining area",when the replacement method of the double-seam working face is "skip mining between mining areas",the surrounding rock stress at the mining roadway of the lower coal seam is small.It is clear that the stress influencing factors of the strong rock pressure behavior in the mining of extra-thick coal seams include the lateral abutment pressure of the upper section of the working face,the coal pillar of the upper coal seam and the advanced abutment pressure of the working face.It is determined that the working face replacement mode suitable for the "Carboniferous Permian" coal seam mining in Xiaojiawa Coal Mine is inter-mining skip mining.(2)The structural model of the overlying rock along the goaf side and the mechanical model of the lateral abutment pressure generated in the lateral coal body of the fully mechanized top-coal caving mining roadway in the extra-thick coal seam are constructed,and the lateral stress transmission mechanism of the additional load of the overlying rock is revealed,and the additional load of the strata in the collapse zone,the fracture zone and the bending subsidence zone are obtained respectively.The superimposed principle of additional stress produced by the lateral coal body of each layer of strata is studied.The influence of the left coal pillar on the disturbed area of the underlying coal seam is analyzed.The width of the disturbed area of the coal pillar stress increases with the increase of the left coal pillar width,and the increase is the same;The distribution characteristics of the advance abutment pressure of the mining face in the thick coal seam under the upper coal pillar are obtained.The high stress of the floor at the upper coal pillar and the advance abutment pressure of the stope are high stress superimposed areas,and the disturbance width of the superimposed stress area is the largest along the peak point of the abutment pressure in front of the stope.It is determined that the stress driving factors of the strong rock pressure behavior in the mining roadway of Coal Seam 13 # are the lateral abutment pressure of the working face in the upper section of Coal Seam 13 #,and the transfer load of the remaining coal pillar of Coal Seam 8 #.(3)Based on the principle of stress superposition,the mechanical model of stress distribution in the roadway floor is established,and the stress expression at any point of the roadway floor is obtained.Based on the theory of slip line field,this paper expounds the mechanism of flowing floor heave and broken floor heave of soft strata in the floor under the condition of fully mechanized top-coal caving mining in extra-thick coal seam,gives the criterion of floor deformation and instability,and determines the maximum depth of floor slip failure.It is concluded that the type and failure form of the material trough floor heave in Xiaojiawa Coal Mine is the fracture type of the roadway concrete floor caused by the fluidity of the floor mudstone.The mechanical model of floor slotting pressure relief is established,and the preliminary scheme of floor slotting pressure relief is proposed to weaken the appearance of strong rock pressure.The reasonable slotting depth and width of Xiaojiawa Coal Mine are deduced.It is concluded that when the floor slotting is completed,the floor heave value is significantly reduced.Before the influence of the advance bearing pressure,the floor heave value is expected to decrease by 30.57%～44.94%.When the influence of the advance bearing pressure,the reduction range is reduced.(4)The technical system of "bolt(cable)support parameter optimization+roadway floor cutting and pressure relief+working face layout optimization" is proposed for the treatment of strong rock pressure in the mining roadway of Xiaojiawa Coal Mine No.13 Coal Seam.The support form of bolt+anchor cable+steel belt+net for the roof-side-bottom of the goaf roadway in the No.13 coal seam of Xiaojiawa Coal Mine was determined and the support parameters were optimized.The reasonable width of the pressure relief groove was0.5m,the reasonable reserved width of the narrow coal pillar was 10.83 m,and the staggered distance between the mining roadway and the remaining coal pillar was42.5m.The appearance of strong rock pressure in the mining roadway of No.13 coal seam in Xiaojiawa Coal Mine has been greatly improved. |
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