Study On Gob-side Entry Retaining Technology With Cutting Roof And Releasing Pressure In Super High Roadway Of Fully Mechanized Coal Mining Face

In order to deal with the connection of excavate and grub,eliminate the stress concentration of the coal pillar,Study on gob-side entry retaining technology with cutting roof and releasing pressure was carried out in 3302 Return roadway of Sangshuping No.2 Coal Mine.In the experiment,some methods such as theoretical analysis,numerical simulation,field test and field measurement were adopted to study the characteristics of roof structure,cutting parameters,surrounding rock control technology and equipment,and the laws of strata behavior for the gob-side entry.Finally,gob-side entry retaining technology based roof cutting and pressure relief which are most applicable to super high roadway of fully mechanized coal mining face.The field test showed that the effect of retaining roadway along gob was good.The main research results are as follows:First,the analysis of roof breaking process shows that the roof structure can be regarded as a short cantilever beam in a certain period of time after roof caving.The mechanical analysis of short cantilever roof structure shows that the main factors affecting the stability of roadway roof are the size of broken rock blocks of“small structure”,the size and the rotation angle of broken rock blocks of “big structure”,the bearing characteristics of gangue in goaf,and the bearing characteristics of coal rib.Second,reasonable cutting height and angle were studied by theoretical analysis and numerical simulation analysis.As a result,the cutting parameters and pre-splitting blasting parameters were determined as follows:the cutting height is 8m,the cutting angle is 10 degrees inclined to the side of goaf,the distance between the blasting holes and coal rib is 4400 mm,the distance between the blasting holes is 500 mm,the diameter of the blasting holes is 42 mm,the blasting mode of slit charge and the blasting structure of “3+3+2+2”charge are adopted,the charge quantity per hole is 3kg.Third,based on the distribution characteristics of surrounding rock plasticity zone and roof structure characteristics of gob side entry with cutting roof and releasing pressure,the train of thoughts on surrounding rock stability control was putted forward.As a result,the bolt-cable support technology was adopted to reinforce the surrounding rock of the roadway.The steel tubular pillars filled concrete with adjustable height and the super-high folding bracket were used as temporary strengthening support equipment in super-high gob-side entry.Based on the Principle of blocking air leakage channel,the inorganic composite sealing material were used to spray gangue wall in roadway for solving the problem of air leakage.Fourth,based on the analysis on deformation characteristics of surrounding rock and the force characteristics of supporting structure,the conclusion was drawn that different sections of roadway in the whole process of gob-side entry retaining can be divided into advanced pressure affected area,dynamic pressure affected area,dynamic pressure affected eased area and pressure stable area.When gob-side entry was in stable period,the convergence of roof to floor was about 605 mm,and the deformation was 10%~12% of the original height of the roadway;The distance convergence of roadway sides was about 535 mm,and the deformation was 12%~13% of the original width of the roadway.