Study On The Theory And Technology Of Gob-side Entry Retaining Under The Condition Of Large Dip Angle Of Thick Coal Seam

After the mining of the large dip angle coal seam,the complicated mine pressure evolution laws have seriously restricted the application and promotion of gob-side entry retainingtechnology.In order to solve the gob-side entry retainingsurrounding rock’s stability issues of the large dip angle thick coal seam,this paper adopts the research means combining analog simulation,theoretical analysis,numerical analysis and field test,starts with research of the mine pressure evolution laws after the mining of the large dip angle coal seam,analyzes the mine pressure environment of the retaining surrounding rock,puts forward measures such as roadway-side support and entry-in support pointedly,validates the stability of surrounding rock in key retaining areas through analog simulation,and brings forth support measures pointedly in accordance with the field geology and production condition through,as well as through observation of mine pressure,analyzes the deformation law of surrounding rock and summarizes the retaining roadway support principle.Through a series of researches,this paper comes to main conclusions as below:(1)The mine pressure laws within the working face of the large dip angle thick coal seam are: a.the support pressure distribution in front of working face has the law of asymmetry;b.the weighting strength in different areas of the working face has the law of asymmetry;c.the first weighing and periodic weighting of the working face have the law of time sequence;d.the activity level of overburden strata movement has the characteristic of asymmetry.The variation of stresses at the lower end is affected by the mine pressure in mining field and its law has distinct segment characteristics: gradation loading phase,sub-gradation loading phase,and constant load phase.After the structure of main key stratum in mining field has been affected by weighting for many times,its break law represents the “O-X” break form.The lower end takes the failure model of tension-shear as its main failure mode,and develops a relatively complete curved tri-angle lump.(2)Regarding the roadway-side support issues of upper waste rock impact above the large dip angle coal seam,roadway-side block rock facility fit for the large dip angle thick coal seam has been designed,whose strength is validated to meet design requirements through strength check.In addition,the mechanical testing has been carried out for roadway-side bearing structure,which has researched the mechanical loading mechanism and uniaxial strength of waste rock bearing,gelatinization heap with high stone content,high polymer material concretion waste rock test specimens,which are all regarded as up to requirements for retaining roadway-side bearing of roadway-side bearing the large dip angle coal seam.(3)The discourse of the action mechanism of complete bolting support system is relatively detailed,and the research shows that the complete bolting support system acts on rock test specimens,and is capable of enhancing anti-pressure ability,shear-bearing capacity,bending resistance ability and creep-resistance ability of test specimens remarkably.(4)It shows through the plane strain analog simulation serial tests that,under the condition of waste rock applied for filling and bearing and surrounding rock intensity enhanced properly,the key retaining areas could maintain the stability.And it analyzes the stability of the key retaining blocks in theory.(5)Appropriate support measures are adopted,the retaining roadway of the large dip angle thick coal seam could meet the need of secondary utilization and according to field experience,it sums up the controlling principle of surrounding rock: change support thought,enhance support quality;attach importance to the role of ‘support’;keep gob-side roadway roof intact,without the cut of roof;observe closely and reinforce in time.