Research On Surrounding Rock Control Technology For Gob-side Entry Retaining In Top-coal Caving Of Gently Inclined Coal Seam

China is a big coal producing country and a big coal consuming country.The abundant coal resources have injected a steady stream of power for the development of China's industrial economy.However,after a long period of large-scale mining,the amount of coal resources has dropped sharply.In order to ensure the sustainable development of China's industrial economy,it is imperative to increase the recovery rate of coal resources and avoid waste of resources.The technology of gob-side entry retaining has also been vigorously promoted.However,the technology of gob-side entry retaining is mostly used for near-horizontal coal seams,There are less research on the top-coal caving of gently inclined coal seam.Therefore,carrying out research in this area has an important engineering application value.This paper takes the gently inclined fully mechanized caving face of No.10 coal seam in Nuanquan Coal Mine as the research background.Firstly,it conducts on-the-spot investigation to understand the production situation of the working face and collects the distribution and mechanical properties of the top and bottom rock layers.Secondly,the activity routines of the surrounding rock during the staying along the goaf is studied,and the mine pressure calculation model of the roadside support body is constructed based on the site geomechanical conditions.At the same time,the support parameters of the roadway and the lane are designed.Then the numerical simulation method is used to verify the feasibility of the proposed surrounding rock control scheme;Finally,the effect of gob-side entry retaining is evaluated through the mine pressure observation in the field test.The main results of the paper are as follows:(1)By analyzing and studying the law of surrounding rock activity during the process of retaining roadway along the goaf,and the law of the deformation of surrounding rock and distribution of mine pressure during the roadway retaining along the goaf is initially discovered.At the same time,combined with the geological conditions of No.10 coal seam in Nuanquan Coal Mine,the calculation model of mine pressure along the goaf is established.(2)According to the analysis of the factor of the dip angle of the coal seam affecting the stability of the roadway along the goaf,it is concluded that the greater the dip angle,the greater the tangential force of the roadside support body from the upper rock stratum,which is more detrimental to the stability of the roadside support body.Therefore,the influence of this factor should be fully considered when designing the support of the side road backfill.(3)Through the analysis of the action of the side support body and the actual situation,it is determined that the soft concrete continuous wall is used as the roadside support body.The design wall has a width of 1.2 m,the concrete with the designation C30 is selected,and the transverse anchors with a spacing of 800 mm are applied for reinforcement.At the same time,after analyzing the performance requirements of the support in the lane,it is determined that the basic support in the lane is supported by anchor nets and the parameters are designed.(4)After analyzing and sorting out the data collected from the on-site investigation,the numerical simulation of the 10107 transport chute in the Nuanquan coal Mine is carried out using computer numerical simulation software.The results show that under the condition of design support scheme,the 10107 transport chute can meet the requirements of safe recovery of the working face and the lower working face.(5)In the industrial test,according to the actual situation of the Nuanquan coal Mine,the filling process is designed,and the main equipment is selected and calculated.At the same time,from the on-site ore pressure observation data,it is found that the maximum displacement of the top and bottom of the roadway is 285 mm,and the maximum displacement of the two gangs is 302 mm,which are all within the safe allowable range,and the effect of retaining the roadway is good.From the perspective of economic technology,it is concluded that the use of roadway retaining technology has not only alleviated the conflict of mine mining succession,but also obtained economic benefits of more than 81.87 million yuan for each coal pillar.