Study On Surrounding Rock Control Technology Of Roadway Protection With Small Coal Pillar For Roof Cutting And Pressure Relief In Thick Coal Seam

My country has large reserves of coal resources in thick coal seams,but for a long time,due to the limitation of production technology and the need for safety of underground workers,most mines have implemented wide coal pillars for road protection mining,resulting in low coal recovery rate and serious resource waste.Small coal pillar roadway protection technology can effectively reduce the waste of coal pillar resources,but small coal pillars often face serious mining pressure problems such as mining impact,coal pillar stress concentration,and large deformation.Therefore,how to efficiently produce and quickly replace mining has important research significance for coal pillar stability and surrounding rock control in fully mechanized caving mining in thick coal seams.Roof cutting and pressure relief is the implementation of directional cracking and slitting technology in the advanced distance section of the working face,which has outstanding advantages in solving the problems of the length of the roof cantilever beam and the stress concentration of small coal pillars.The effect has a significant impact.Based on the research background of the 10102 fully mechanized caving face return airway of Lvliang Fujiayan Coal Industry,this paper adopts various methods such as numerical simulation,theoretical calculation and field industrial test to analyze the migration law of overlying rock structure,the occurrence law of rock pressure and the discharge The rationality of coal pillar width and the key parameters of roof cutting and pressure relief are systematically analyzed from the aspects of pressure effect,etc.The main research contents and results are as follows:(1)Through the analysis of the serious deformation of the coal pillar in the adjacent working face section,it is found that the unreasonable width of the coal pillar is likely to cause excessive deformation of the surrounding rock of the roadway and the problem of poor coal pillar stability.Reasonable,it is difficult to effectively control the surrounding rock control problem under the influence of mining.(2)By establishing the mechanical model of the basic top key block and coal pillar bearing,the mechanical analysis of the fracture position of the key block and the bearing relationship of the coal pillar is carried out.Correlation,the larger the fracture rotation angle of the key block,the lower the load of the coal pillar in the goaf is when the fracture is located.By deriving the relational expression of the basic roof caving step distance before and after the roof cutting,it can be seen that the basic roof breaking step distance decreases with the increase of the number of simply supported sides.Three-sided fixed support,the three-sided fixed support after the initial collapse becomes two-sided fixed support,the caving step distance decreases correspondingly after the top is cut,and the mine pressure appearance of the working face also decreases accordingly.Therefore,the basic roof structure of the roof can be artificially changed by means of roof cutting,so as to reduce the load of the coal pillar and improve the stability of the coal pillar.(3)By establishing numerical models of different coal pillar widths,the plastic failure degree,stress peak distribution,and tunnel section shrinkage of coal pillars with different widths are sorted and analyzed.The results show that with the increase of the coal pillar width,the internal stress concentration coefficient of the coal pillar and the deformation of the roadway decrease accordingly,especially when the coal pillar width is 6-9 m,the vertical stress peak value and the stress concentration coefficient of the coal pillar decrease most obviously.After the coal pillar exceeds 9 m,the range of the elastic zone inside the coal pillar remains basically unchanged,the plastic zone is stable at about 35%,and the coal pillar has good stability.Due to the problems of development and air leakage,the designed coal pillar is set to 10 m,which not only meets the safety production problem,but also has a good supporting capacity.(4)Apply numerical simulation to reveal the pressure relief mechanism of the roof cutting parameters on the coal pillar and roadway,compare and analyze the numerical simulation results of key parameters such as different roof cutting depths and angles,and obtain the top cutting depth of 24 m and the roof cutting angle under the geological conditions The 0° roof cutting scheme greatly reduces the stress peak value of the coal pillar and the deformation of the surrounding rock,and the pressure relief effect is obvious.(5)On the basis of leaving a 10 m coal pillar and the optimal roof cutting scheme,the technical scheme for controlling the surrounding rock of the roadway protection by roof cutting and pressure relief and leaving small coal pillars is given.The maximum convergence of the gangway is 295.1 mm,the approaching amount of the roof and floor is 225.8 mm,and the stress of the anchor rod after the surrounding rock is stabilized is between 80 k N～ 150 k N.The force begins to stabilize gradually.The average force of the anchor cable near the coal pillar and the anchor cable near the solid coal gang is 210.5 k N ～ 180.3 k N,both of which are in the range of pre-tightening force,and the roadway roof is basically stable without major deformation.