Research On The Stability Of Coal Pillar And Partition Support Technology Of Roadway Driving Along Goaf Under Strong Dynamic Pressure

Bailiang coal mine is a mine with strong ground pressure,broken surrounding rock and difficult support in Chenghe mining area.In order to solve the problem of tight connection between coal mining and excavation,it has become an inevitable choice to drive along next goaf during the adjacent mining faces.Under the influence of strong dynamic pressure,it is difficult to control the surrounding rock of the roadway,which has become a difficulty in coal mining engineering.Among them,the reasonable size of coal pillar is the key to affecting the stability of roadway.Based on the optimal size of coal pillar,the independent support is designed through dynamic pressure zoning,and the control effect of zoning support design is evaluated through on-site monitoring.The research shows that:(1)The plastic zone of surrounding rock is severely damaged due to the comprehensive impact of mining and excavation.When the width of the coal pillar is 5m,the plastic zones on both sides of the coal pillar are overlaped,and the coal pillar is completely plastic.The plastic zones on both sides of the coal pillars with widths of 10m and 15m are connected but not completely connected.The plastic zones on both sides of the coal pillar with a width of 20m are far apart.The coal pillar width enters the plastic zone within 5m～15m,but no damage occurs.The displacement and plastic zone of the coal pillar with a width of 10m are the smallest,which is a reasonable width of the section coal pillar.Based on plastic analysis,simulation results,limit inference,practical experience and geological conditions,the coal pillar is finally determined as 9m.(2)According to the extent of 516 transportation roadway affected by the mining dynamic pressure of adjacent working face,it is divided into three sections:long-distance weak disturbance section,short-distance dynamic pressure overlapping section and later roadway excavation along the goaf.Based on the theory of self stable invisible arch,the surrounding rock support parameters of dynamic pressure gob driving roadway are designed in different areas.The design uses the high conversion efficiency of torque preload of left-hand high-strength deformed steel bolt,the designed bolt preload is not less than 220N·m and the anchoring force is not less than 105kN.According to the theory of self stabilizing invisible arch,the height of potential caving is calculated,and then the pre tightening force of anchor cable is determined to be 120kN.The diameter,length and row spacing of anchor rod and anchor cable,as well as the model of tray and steel belt shall be selected according to different sections to ensure that the support parameters are positively correlated with the severity of dynamic pressure disturbance.(3)The partition support effect of 516 transportation roadway can be seen that in the long-distance weak disturbance section and the short-distance dynamic pressure overlapping section,with the gradually decrease of the distance between 516 transportation roadway and 518 fully mechanized mining face.It is obviously and violently affected by mining,and the deformation of the coal pillar is significantly greater than that of the side.The overburden can control the stability of surrounding rock.In the narrow coal pillar of roadway driving along goaf,with the gradual increase of the distance between the trench excavation and the adjacent working face,the collapse movement of the overlying strata is basically stable,and the cumulative coal pillar deformation is relatively small.The designed partition supports are reasonable,which ensure the safety and efficiency of 516 heading face and 518 mining face,and provide certain technical support for mining and roadway excavation of similar working faces.