Study On Surrounding Rock Control Technology Of Gob Side Entry With Small Coal Pillar Of Laoyaogou Coal Mine

Gob side entry with small coal pillar can improve the recovery rate of coal resources,outstanding economic benefits,has been used more and more in recent years.But the geological conditions of our mine is complex and changeable,some mines’coal pillar setting is unreasonable,roadway support effect is poor,the problem is more prominent under the condition of inclined coal seam.Based on the project background of 20202 working face return air roadway in Laoyaogou Coal Mine,this study adopts the methods of laboratory experiment,theoretical analysis and numerical simulation,centering on the overlying rock structure,reasonable width of coal pillar and surrounding rock control of gob side entry,and researches the surrounding rock control technology of gob side entry with small coal pillar.The main research results are as follows:（1）Summarize the general situation of 20202 working face return air roadway engineering and analyze the damage reasons of roadway surrounding rock;The physical and mechanical properties of coal rock are tested,and the physical and mechanical parameters obtained can provide reference for the subsequent theoretical calculation and numerical simulation.The deformation and failure test of coal rock under different dip angle,it is concluded that dip angle has obvious weakening effect on coal sample strength.（2）Based on the geological conditions of Laoyaogou coal mine,the movement and structure of overlying rock in gob side entry and the location of basic roof fracture are analyzed;The mechanical model of gob side entry with small coal pillar in inclined coal seam is established.By calculating the width of plastic zone on both sides of coal pillar,it is preliminatively obtained that the width of coal pillar should be greater than 7.23m.Based on the analysis of the necessity of top cutting and pressure relieving,it is concluded that in order to improve the stress environment of the roadway surrounding rock and ensure the success of small coal pillar excavation along the gob,top cutting and pressure relieving should be carried out in advance.（3）FLAC^3Dnumerical software is used to establish the three-dimensional calculation model of gob side entry with small coal pillar.Through numerical calculation,the distribution law of lateral abutment pressure at the edge of goaf is obtained.The distribution law of stress,displacement and plastic zone of roadway surrounding rock under different coal pillar width scheme is simulated and analyzed.Combined with the theoretical calculation results,the reasonable coal pillar width is finally determined to be 8.0m.（4）In view of the geological condition that 20202 return air roadway is located in inclined coal seam and there is hard and thick rock layer above the roof,in order to improve the stress environment of roadway surrounding rock,a roof cutting and pressure relieving scheme is designed for hydraulic fracturing in 20201 track roadway;Based on multi-stage support,truss support and asymmetric support,the roof and wall collaborative support technology is proposed,and the optimal support scheme of20202 air return roadway is confirmed by theoretical calculation and numerical simulation.The numerical simulation analysis of roadway surrounding rock deformation of the original support scheme and the optimized support scheme confirms the feasibility of the optimized support scheme.（5）Carry out field industrial tests.By monitoring the effect of hydraulic fracturing,can see that hydraulic fracturing has a good effect and artificially creates a weak surface in the hard rock formation.According to the mine pressure monitoring values,the optimized surrounding rock control scheme can effectively control the harmful deformation of roadway surrounding rock and solve the problem that the roadway needs to be maintained repeatedly.The thesis has 64 figures,11 tables,and 95 references.