Research On Mining Working Face Cross Oblique Empty Roadway Stress Distribution Laws And Migration Regularity Of Surrouding Rock

Compared with developed countries,China's current coal resources waste is very serious.Our resource recovery rate is very low.Shanxi province is an important coal industry base in China.From the 1980s and 1990s,due to the mining technical limitations,and the downturn in the coal market,a large number of small-sized mines use methods of room-and-pillar mining or lane-open mining.Residual coal mining can not only improve the economic efficiency of enterprises,but also prolong the service life of old mines.At the same time,residual coal mining has important significance of building a harmonious society and protecting the ecological environment.This thesis focuses on the Shanxi Coal Group of China Coal Seam No.3,using residual coal mining work as the engineering background,and exposes the old data and 3101 residual mining.This thesis summarizes the existing structure of the residual coal,studies rock roadway stability and distribution rule of surrounding rock and migration law in the process of residual mining,using theoretical analysis,numerical simulation,simulation and other means of research.The thesis raises the occurrence of text structure,puts forward related suggestions to improve supporting,sums up the impact of the intersection angle to the surrounding rock,and gives the stress distribution law of oblique roadway and the migration law of oblique roadway roof.The main work is as follows:1.Analyzed residual coal occurrence structure of Shenghua 3#coal seam old mining area,and took the structure into five types,and determined that old mining area occurrence situations mostly contained abandoned roadway and pillar.2.Theoretical study of the residual working face cross oblique empty roadway surrounding rock shows:the support pressure in coal pillar turns gradually from "asymmetric saddle" of wider coal pillar into "inclined pillar",then into "parabolic-kind type" when plastic zones on both sides of coal pillar cut through.On residual working face cross oblique empty roadway with the existence of triangle coal pillar,the overlying strata pressure presents asymmetric distribution with the front coal body;Inclined alley and mining roadways are in advance mining influence scope,and the intersection overhang area is large,easy to be destroyed;Junctions tend to form with acute triangle coal pillar,so the stress concentration is intense,exacerbating the destruction of the surrounding rock at junctions.3.Numerical simulation method was applied to study working face cross different angles of oblique alley.Through working face cross oblique empty roadway stress distribution analysis and plastic zone analysis,we know that:(I)Working face cross oblique roadway,the smaller the alley angle,the greater the stress concentration coefficient of triangle coal pillar,and the greater the plastic failure zone is.Thus,the smaller the empty roadway angle,the harder working face cross empty roadway is.(2)Working face cross empty roadway with angle,coal pillar stress in the front of the roadway is asymmetrical distribution along the direction of working face.Of the working face stress near the left side of the gateway is higher;stress near the right side of the gateway is lower.The reason is that front coal pillar of the oblique roadway gets in advance under the working face roof,bears the load of the strata,and improves the stress distribution of the coal pillar.This is also one of the reasons why oblique roadway is relatively easy to control.(3)The cross angle exerts the greatest influence on the scope of the need to strengthen the supporting of roadway surrounding rock,because with the change of the cross angle,roadway roof bare area changes,the area of the triangle changes,roadway intersection shape changes,roof breakage exacerbates two sides damage,and the surrounding rock of the area turned deformed even complicated further at the same time.Combining the influence law of anchorage mode,when the roadway intersection angle is acute or obtuse angle,we should focus on strengthening the triangle zone surrounding rock support,particularly in the region of acute angle intersection.4.Similar material simulation was applied to simulate the mining working face cross oblique empty roadway.Systematic study was made on surrounding rock failure,stress distribution and roof movement law when the residual coal mining face crosses oblique roadway.Following conclusions are made after analysis:(1)In entity coal mining,coal body,top coal and direct top roof have minimum stress concentration coefficient;when working face is near the empty roadway,the stress concentration coefficient takes second place;when mining face comes to coal pillar,the coal pillar,top coal,and direct top roof have maximum stress concentration coefficient.(2)When working face crosses oblique empty roadway,adjacent pillar stress transfer occurs later,which means that range of influence of mining face advanced mine is far less than mining working face cross parallel empty roadway.Such experimental result fully verifies that when work face crosses oblique empty roadway,front coal pillar getting into under the roof in advance slows down the coal pillar deformation and failure.(3)Compared with working face cross parallel empty roadway,oblique front coal pillar getting into under the roof in advance bears the load of overlying strata,provides timely support on the roof,and improves the stress condition of the coal pillar.This oblique empty roadway distribution,compared to parallel mine roadway whole roof breaking,greatly reduces the possibility of working face roof accident.(4)Working face cross oblique roadway and roadway timbering advance distance should be no less than 30m.In repeated mining face crossing roadway process,large area pressure frame of the working face and roof accident easily occur in the process of coal pillar mining.The advance distance of coal pillar reinforcement of working face cross two oblique empty roadways should be no less than 40m.(5)Through analysis of the movement and deformation law of overlying strata on oblique empty roadway mining,due to the formation of working face and roadway in a certain angle,the time of stand into roadway time is inconsistent,the direct top roof of empty roadway receives different pressure influences by advance abutment,oblique roadway destruction is partial and segmented,oblique roadway in advance upon working face roof movement does not increase significantly,and it is much smaller compared to the parallel roof movement.Even if there is destabilization if the coal pillar,the triangle coal body in the front of roadway can still support the formation of the roof.