Research On Gob-side Entry Retaining Technology For Roof Cutting And Pressure Relief In Fully Mechanized Mining Face Of Thick Coal Seam

As a traditional coal mine roadway protection method,coal pillar retention has the defects of serious waste of resources and high maintenance cost of roadway.Although gob-side entry retention technology improves resource utilization to a certain extent,for thick coal seams with large burial depths,it is prone to serious side drums,high bottom drums,serious deformation or even failure of filling and support bodies,and difficult roadway maintenance.question.Based on this,this paper adopts the method of combining theoretical calculation,numerical simulation and field test to study the mechanism of roof cutting and pressure relief,and proposes a gob-side entry retention scheme for roof cutting and pressure relief.The field application results show that the gob-side entry retaining scheme of roof cutting and pressure relief can significantly reduce the deformation of the surrounding rock of the roadway and reduce the internal compressive stress in the small structure of the surrounding rock.The main research contents and results of this paper are as follows:(1)The roof migration situation was analyzed for the two cases of roadway retention without roof cutting and roof cutting.It was found that the overlying strata of the roadway retention formed internal and external stress fields after mining with the working face.When the internal elastic-plastic boundary line moves inward,the range of the internal stress field increases,and the masonry beam structure tends to move upward.The higher the top-cut height,the lower the peak value of the bearing stress in the coal wall and the larger the range of the internal stress field.When the top-cut height reaches a certain position,the peak value tends to be stable.Through theoretical analysis,it is concluded that the support resistance of the backfill body beside the roadway is lower after the gob-side entry retaining roof is cut than when the roof is not cut,and the entry retention is more stable.(2)Numerical simulation is used to study the on-site working conditions of roof cutting entry retention,setting entry retention models with different roof cutting heights,different roof cutting angles and different filling body widths,and monitoring the surrounding rock deformation of the roadway and the supporting resistance of the filling body respectively.The monitoring found that the deformation of surrounding rock and support resistance decreased first and then stabilized with the increase of the top-cut height,increased with the increase of the top-cut angle,and decreased with the increase of the backfill width.And it is concluded that: the roof cutting height needs to meet the cutoff area roof can fill the gob on the side of the roadway through the crushing expansion of the rock,and the crushing expansion of the gob on the side of the roadway is greater than that in the middle of the gob.This engineering background calculation adopts The top-cutting height of 20.5m is better;the top-cutting angle needs to satisfy factors such as the rapid collapse of the roof and the minimum disturbance to the roadway,and it is better to use the top-cutting angle of 5°;For air volume requirements,it is better to use a width of 1.5m.(3)After applying the theoretical calculation and numerical simulation results to the field,it is found that the deformation of the surrounding rock of the entry retaining after roof cutting is basically consistent with the numerical simulation.After the roof is cut,the moving amount of the roof and floor of the roadway is maintained at about 634.5mm,and the moving amount of the two sides is maintained at about 326.5mm,which is about 56% less than when the roof is not cut,and the moving amount of the two sides is reduced by about 56%.72%.The change trend of the on-site monitoring data shows that the gob-side entry retaining can reduce the extrusion deformation of the surrounding rock of the roadway and reduce the extrusion stress in the small structure of the surrounding rock.After cutting the roof and retaining the entry,the loose circle was monitored,and it was found that the range of the loose circle increased by about 0.234 m,and the increase was small,indicating that the internal damage of the surrounding rock was small after the roof was cut and the pressure was relieved.Industrial tests have proved that the deformation of the surrounding rock of the roadway after roof cutting is small,and the expected research results have been achieved,which has certain guiding significance for the improvement and optimization of the gob-side entry retention technology for thick coal seam roof cutting and pressure relief in the future.