| The deformation and failure of surrounding rock of roadway is affected by many factors such as the depth of mining,height and thickness,and it is also closely related to the fracture structure of main roof.However,due to the asymmetry and heterogeneity of surrounding rock structure,the surrounding rock of gob-side coal-rock roadway in inclined coal seam widely distributed in Guizhou shows more serious deformation and failure characteristics under the influence of mining disturbance,which seriously affects the normal mining replacement and intelligent mechanization transformation and upgrading.Based on the engineering background of 151608 return airway in a mine in Guizhou,the thesis systematically studied the stability of surrounding rock of gob-side coal-rock roadway in gently inclined coal seam under different main roof fracture forms by means of indoor mechanical experiment,theoretical analysis,numerical simulation,similar simulation experiment and field measurement.The reasonable width of coal pillar in 151608 return airway during subsequent excavation was determined,and the following main research results were obtained:(1)The deformation of roadway surrounding rock under the original excavation scheme of 151608 return airway in a mine in Guizhou was summarized and analyzed based on the field investigation.The physical and mechanical parameters such as compressive strength and tensile strength of the roof and floor of 151608 return airway and its coal seam were obtained by laboratory test.(2)The spatial structural mechanics model of overlying rock in gob-side coal-rock roadway in gently inclined coal seam was established,and the calculation formula of the fracture position of the main roof was deduced.According to the relative spatial position relationship between the fracture line and the roadway and coal pillar,four kinds of lateral fracture forms of the main roof of the gob-side coal-rock roadway in gently inclined coal seam were proposed,and the calculation formula of coal pillar load under different fracture forms was further deduced.The lateral fracture of different main roofs was simulated.The results showed that the fracture of the main roof above the roadway had the greatest influence on the overall stability of the surrounding rock and coal pillar,followed by the coal side,coal pillar,and the fracture of the gob side had the least influence.(3)The theoretical calculation results showed that the fracture position of the main roof is 3.76 m from the edge of the gob in the upper working face,and the field drilling detection result was 3.92 m,which verified the reliability of the theoretical calculation.Through the mechanical experiment,the similar material ratio of the’rock-coal-rock’ combination specimen was determined,and the specimen was loaded.It was found that the peak strength of the specimen increased with the increase of the width of the coal pillar,and the time for the specimen to reach the peak strength was basically extended.The deformation generated was decreased accordingly when the specimen reached the peak strength,and the smaller the width of the coal pillar,the greater the total displacement generated after the specimen was loaded.(4)By simulating the deformation and failure law of roadway surrounding rock under different coal pillar widths,it was concluded that with the increase of coal pillar width,the plastic zone of surrounding rock,the deformation of roadway roof and floor and their two sides,and the vertical stress of both sides gradually decrease,and the interval between roadway surrounding rock and plastic zone of gob side of upper working face gradually expands.At the same time,the width of coal pillar was larger,the stress peak range of right side from roadway was farther,which was more conducive to roadway stability.When the width of coal pillar was 5m,the surrounding rock of the roadway and the plastic zone of the gob were not connected,and the stability of the roadway was relatively good.Comprehensive research shows that it was reasonable to determine the width of the subsequent coal pillar of 151608 return airway as 5m.(5)The engineering test was carried out on the 5 m wide coal pillar in the subsequent excavation process of 151608 return air roadway.Through field observation and drilling detection,it was found that the roadway contour was complete at the same distance after the optimization of coal pillar width,and the support of U-shaped shed did not produce large deformation.The inner wall of the borehole was smooth and there was no collapse hole,and the roadway maintenance condition was relatively good,which indirectly proved the reliability of the method for determining the reasonable coal pillar width of gob-side entry in gently inclined coal seam. |
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