Research And Application Of Gob-side Entry Retaining In JinFeng Large Mine Height Coalface

With the intensive development of coal mining,the technology of retaining roadway without coal pillars has been widely applied.The flexible mould concrete support technology is helpful to solve the low support resistance,poor shrinkage,poor airtightness and difficult maintanance in the later stage of the roadway without coal pillars,which is of great significance for the coal mining without large coal mining face.The paper uses the comprehensive research methods such as experimental test,theoretical analysis,numerical simulation and on-site industrial test to carry out a systematic study on the gob-side entry retaining of large mining height technology in Jinfeng Coal Mine.The main research results are as follows:(1)The deformation speed and strength of surrounding rock in gob-side entry of large mining height are mainly affected by the advance distance and mining dynamic pressure of fully mechanized working face.The width and intensity of the roadway are important factors determining the stress distribution of the surrounding rock.The maximum support load of the design gob-side entryretaining is mainly based on the law of the front stage movement,and the maximum support deformation of the design roadway along the main road is mainly based on the late stage activity of the roof.(2)The gob-side entryretaining of large mining height working face adopts "anchor,net,cable,spray" support and advanced reinforcement support adopts "one beam and three columns" shed and steel belt;the roadside support adopts "the front netting+cantilever?-type steel beam+ flexible mould concrete wall+wooden point column"combined support.The flexible formwork concrete(specification:lengthxwidth×height=3mxlm×3.5m),and the concrete mix ratio is cement:sand:gravel:water:fly ash:admixture=1:1.77:1.88:0.50:0.31:0.003;The concrete strength is C25;Lagging reinforcement support adopts "one beam,three columns" shed and wood stack support.(3)Flexible mould concrete wall of gob-side entryretaining of the large mining face has early surge resistance and higher compressive strength.The three stages of surrounding rock deformation are:initial small deformation stage of surrounding rock(0-15m);severe stage of surrounding rock change(15-35m);surrounding rock changes stage that is tend to stabilize(after 50m).Therefore,when the working face is 15-30m after mining,it is necessary to strengthen the roof reinforcement and temporary support,which is conducive to maintain the stability of the roof.The research results of the thesis have been successfully applied in the 011805 working face in Jinfeng Coal Mine,and have created good social and technical economic benefits.