Cumulative Energy Instability Characteristics And Reasonable Size Of Coal Pillar In Fully Mechanized Caving Face

Leave districts section of the coal pillar has been widely used in mining,coal mining has a separate the mined-out area,the action of protecting roadway,however section design is not reasonable coal pillar under high stress concentration and working face mining disturbance instability disasters emerge in endlessly,has been a serious threat to working face safe and efficient mining,so need to segment instability and reasonable shaped coal pillar size problem is studied.According to section under dynamic and static stability of coal pillar problem,in this thesis,based on domestic and foreign scholars study by field investigation and theoretical analysis,numerical simulation and the method of micro laboratory section to fully-mechanized sublevel caving mining working face coal pillar shaped instability characteristics under different stress environment,analysis of the dynamic and static load under the action of energy response characteristics and instability mechanism,At the same time,the coal pillar size is optimized,and the corresponding stability prevention and control technology and prevention and control strategy are proposed.The specific conclusions are as follows:(1)The limit energy of section coal pillar is a quadratic function of lateral stressσ3.The lateral stress of section coal pillar at the rear of the working face presents an“upward convex” symmetrical distribution.The stress is positively correlated with the plastic zone and the effective bearing width of section coal pillar,and negatively correlated with the lateral pressure coefficient.(2)The elastic energy of coal pillar in the rear section of the working face presents a bimodal distribution,and the peak stress gradually changes from the air side to the mining side and becomes approximately equal with the advance of the working face.The peak value of the vertical stress of the coal body in front of the working face is 14 m in front of the solid coal.The distribution of the elastic energy density of the coal pillar in front of the working face decreases gradually with the increase of the distance from the working face,reaching the maximum value in the range of 20 m in front of the working face,and the instability area is located at the side of the coal pillar.(3)The dynamic instability satisfies the requirement that the energy released per unit time is greater than the energy dissipated by coal,while the static instability satisfies the requirement that the energy released per unit time is less than or equal to the energy dissipated by coal;Under dynamic load,the distribution range and peak value of high vertical stress are increased,mainly located in the middle of the coal pillar near the mining side.The distribution trend of elastic energy is similar to that of vertical stress.The peak value of elastic energy is located in the coal pillar 15～20m away from the upper goaf,and the range of plastic zone increases gradually from roof to floor.The negative difference between coal pillar limit energy and elastic energy represents the risk of dynamic instability.The negative difference of roadway side energy under dynamic load is relatively high,indicating greater impact risk here.(4)calculated by theoretical working section reasonable coal pillar size range from8 to 20.56 m,by numerical calculation comprehensive considerations load-bearing characteristics of coal roadway surrounding rock deformation and draw reasonable coal pillar size range is 8 ～ 12 m,seepage analysis penetration coal pillar width is about 6m,combined with supporting validity determine reasonable waterproof coal pillar width 10 m or higher.Finally,the reasonable coal pillar size is 10 m.(5)the large diameter borehole pressure relief and the method of deep hole blasting roof to prevention and control of dynamic and static load,the deployment to microseismic monitoring,monitoring of the deformation of surrounding rock and wall rock stress monitoring of the monitoring system,puts forward 10 m small coal pillar help of rugged,grouting,reinforcing supporting strategies on the coal pillar stability control,Jiang Jiahe coal mine based on the actual effect of prevention and control methods for prevention and control,The results showed that the prevention and control effect was good.There are 62 figures,5 tables and 75 references in this thesis.