Study On Deformation Law And Control Technology Of Surrounding Rock In Close Multiple-seams Roadway

With the rapid development of China's economy,the consumption of coal resources is increasing day by day,and the coal resources with better mining conditions are gradually exhausted.At the same time,coal is still an important pillar to affect the economic and social development of our country for a long time,so it is necessary to exploit some coal seams with poor mining conditions.At this time,the combined mining of close coal seam has become the inevitable trend of close multiple-seams mining.Due to the small distance between the close multiple-seams mining,the mining of the upper coal seam will inevitably cause a certain degree of damage to the roof of the lower coal seam,breaking its original stability and integrity,making the roof of the roadway collapse,leading to the coal mining work can not be carried out normally,and reducing the coal mining rate.In order to ensure the safety and efficiency of mining in close multiple-seams mining,it is important to develop the deformation law of the surrounding rock of the upper and lower mining roadway in close seam,and reasonable safe stagger distance and its surrounding rock control technology.Based on the engineering background of a coal mine in Weinan,Shaanxi Province,this paper studies the deformation of the side of the short-distance coal seam with the interval of 6m by combine the method of theoretical analysis,mechanical model and engineering application,the conclusion is as follows:(1)Based on the elastic theory,the mechanical calculation model of the upper and lower close multiple-seams roadway under the action of the support pressure is established.The stress-strain components of the any coal body within the coal-side were analyzed,and the analytical formulas under the support pressure are obtained.With the help of the elastic-plastic interface coal body in the peak bearing pressure of the "pillar model",the unit coal body with the maximum horizontal tension strain under the action of peak bearing pressure is located at the 0.65 times height of laneway,which was determined by the vertical slice model of the coal body at elastic-plastic interface.The results show that the width of the limit equilibrium zone increases with the increase of the tunnel depth,but decreases rapidly with the increase of the elastic modulus and the ultimate tensile strain of the coal.(2)Based on the support concept of "roof protection first side protection",on the basis of studying the limit equilibrium area and the width of the broken area of the coal side in the close multiple-seams roadway,considering the influence of the coal side fracture on the deformation of the roadway roof,the effective span of the roof is determined by using the pusher equilibrium arch theory of rock mechanics.The mechanical model of plastic failure zone of roadway floor in close multiple-seams under the support pressure of coal pillar is established,and the maximum failure depth of floor under the support pressure is analyzed.(3)Using the stress diffusion theory of soil mechanics,the stress diffusion analysis model of upper coal seam roadway under the support pressure of coal pillar under the condition of internal fault is established.On the basis of the calculation of the range of the limit equilibrium area of the side of the mining roadway in the lower coal seam and the principle that the roadway in the lower coal seam is arranged in the stress reducing area of the coal pillar in the upper coal seam,the safety fault distance of the roadway in the horizontal direction is determined.The results show that the safety fault distance is related to the width of the limit equilibrium zone,the stress diffusion angle and the coal seam spacing.(4)Based on the elastic-plastic analysis of the surrounding rock mass and its dilatancy characteristics,the surface deformation of the surrounding rock mass after the excavation of the upper and lower roadway in the close multiple-seams is analyzed,and the displacement of the upper and lower coal seam's side coal body to the inner side of the roadway after deformation and failure under the roof support pressure is determined,which provides a theoretical basis for reasonably determining the reserved deformation of the side rock body during the excavation of the upper and lower close multiple-seams roadway.(5)Being regarded a coal mine as the engineering background in Weinan,Shaanxi province,the paper calculates the width of the upper and lower side limit equilibrium area,the width of the broken area,the broken range of the top and bottom of the coal side and the displacement of the side of the staggered roadway in the close coal seam by using the above research results.Based on the diffusion analysis model under the abutment pressure of the coal pillar in the upper seam roadway,the safety fault distance of the upper and lower roadway is determined.On this basis,the bolt support parameters of the coal-wall are optimized,and good supporting effects are obtained.The results show that the above research achievements can be used to predict and analyze the coal deformation law of related coal seam roadway.