Study On The Cause Of Shaft Damage And Its Prevention And Control Technology In Coal Mine Protection Pillar Mining

China’s energy endowment of "lacking oil,gas and coal" determines that coal will play a long-term role as the ballast of China’s primary energy.In recent years,with the gradual depletion of coal resources in old mining areas such as Northeast China and Hebei,some coal mines within the coal pillar protected by the industrial plaza have been mined.Shaft damage accidents occur frequently due to coal mining,which seriously threaten the safety of mine production.There are few relevant researches at home and abroad,and the mechanism of the interaction between the overburden strata movement and the shaft caused by the mining pillar is unclear,and the corresponding shaft damage treatment technology is lacking.For this reason,it is of great theoretical significance and application value to carry out the research on the causes and prevention of the shaft damage caused by the mining of the(proposed)Gongguang coal pillar and the mining of the Gongguang protective coal pillar in the coal mine in order to fully tap the potential coal resources,continue the life cycle of the coal mine whose reserves are on the verge of exhaustion,and ensure its safe production.Taking Dashe Coal Mine in Fengfeng Mining Area,Handan City,Hebei Province as the engineering background,the method of combining theoretical analysis,numerical simulation and field measurement is adopted to analyze the movement characteristics of the overlying strata of the mined(to be)protective coal pillar mining and its impact on the shaft stress and deformation,reveal the causes of shaft damage,propose the repair and prevention scheme of the damaged shaft,develop the repair and prevention construction technology,and successfully apply the engineering practice.The main research work of this paper is as follows:(1)By using field observation,geological and numerical simulation research methods,the causes of the auxiliary shaft damage in Dashe Coal Mine are analyzed and revealed.The results show that the maximum surface subsidence of the adjacent auxiliary shaft area caused by the mining of Gongguang Protection Coal Pillar 92606 is 127.4mm,and the maximum vertical compression deformation is 1.48mm/m.The near horizontal circumferential damage of the well at 298m depth is caused by the fact that the shaft passes through a fault at the shaft damage location.When the formation deformation movement caused by the mining of 92606 working face is absorbed and released at the fault location,the relatively large relative movement with the shaft generates the vertical additional force acting on the shaft.Under the combined action of the shaft gravity stress and the additional stress,the shaft is vertically compressed and damaged.(2)Based on the probability integral method,this paper calculates and analyzes the ground settlement caused by the mining of the working face outside the 92606 protected coal pillar on the basis of the ground deformation of the 92606 protected coal pillar.The calculation results show that the maximum settlement value of the ground surface around the shaft under the influence of the superposition of the two is 389.2mm,which is much greater than 168.7mm of the 92606 working face mined separately.In order to prevent the secondary damage of the shaft due to the mining of the new working face,reinforcement and preventive measures should be taken for the auxiliary shaft of the mine before the mining of the new working face.(3)Using FLAC 3D software,the evolution process of wellbore stress was simulated when the 92606 working face was mined without reinforcement after the completion of mining.The analysis shows that when the working face outside 92606 advances to 80m,the stress at the fault position of the shaft starts to rise gradually.After the mining of the working face is completed,the stress reaches 21.01MPa,which is far greater than the ultimate bearing capacity of the shaft,and the secondary damage will occur to the auxiliary shaft.(4)Based on the analysis results of the causes of the shaft damage in the auxiliary shaft of the mine,the prevention technology of "vertical yielding and horizontal resisting" shaft damage is proposed to prevent the secondary damage of the shaft.That is,the additional force is released vertically by cutting the pressure relief groove,and the horizontal bearing capacity of the shaft is increased by erecting the channel steel well ring horizontally.After comparing and optimizing the three schemes for setting the pressure relief groove by using the numerical simulation software,the reinforcement and prevention scheme of grouting behind the wall+pressure relief groove+erecting channel steel well ring is designed.(5)The pre treatment construction technologies for shaft reinforcement,including"grouting behind the shaft wall,cutting pressure relief groove,adding channel steel well ring",have been developed.The field monitoring results show that in the process of mining the 92606 outer working face,the stress and deformation values of the auxiliary shaft after reinforcement,prevention and treatment are within the safe range,and no secondary damage has occurred,which ensures the safety of the mine production and achieves the expected results.Figure[52]Table[16]Reference[83]...