Study On The Safety Mining Technology For Sublevel Caving To The Difficult-to-mine Ore Body In The Northern Mining Area Of Xishimen Iron Mine

Since the easy-to-mine iron deposits have been depleting and the demand for iron ore is increasing with the development of national economy,the difficult-to-mine ore bodies are gradually put into production planning,now,the soft fractured deposits,deposits destroyed by complex mined-out areas and pillar ore bodis are the main component of these difficult-to-mine ore bodies to be mined.It is of great significance for guaranteeing the sustainable development of the domestic iron ore production to solve the technical problems of minging the three types of ore bodies.The northern mining area of the Xishimen iron mine is a typical mine including the three types difficult-to-mine ore bodies,due to the lack of suitable mining technology,these ore bodies have not been effectively exploited.Under the guidance of mine three laws adaptability theory,the sublevel caving mining technologies for high stress fractured ore body,ore body destroyed by complex mined-out areas and pillar ore body are studied separately.By research,the stope structure parameters of sublevel caving method are optimized,the mining sequence and the mined-out area management method are improved,the mining roadway support technology is optimized,and the technical problems about ground pressure control,rock movement control and lean mining of complex residual ore are solved.These research results formed the practical technology of caving method for safe and efficient mining the three types difficult-to-mine ore bodies.The specific research works of this thesis are as follows:(1)Based on the investigation and the stability classification of ore rock,by calculating,the maximum values of critical caving span of the ore and roof rock are 16.7m and 20.2m respectively in mining sublevel,then the synchronous stoping method with double route is proposed,which make the mining time and space adapted to the caving property of ore and roof rock.(2)The flowing parameters of ore granular was determined and analyzed the ore granular flow viscosity,and then combined with the need of ground pressure control,the stope structure parameters of sublevel caving method are analyzed and determined,which improved recovery rate when mining the gently inclined ore body with caving method.(3)The law of ground pressure activity in stope is studied combined with field investigation,statistical analysis and numerical simulation methods,then the mechanism of continuous deformation of roadway,roof falling,convergence of two walls and floor heave are revealed,and proposed a new concept named wedge pressure action zone,at last the support forms of mining roadway are optimized which guaranteed the reliability of the roadway for mining the three types difficult-to-mine ore bodies.(4)On the basis of the above researche results,comprehensive considering the stope structure parameters,roadway layout and mining sequence,selection of shovel handling equipment,excavation and supporting method,ore drawing control and diversion drawing,the forced dig?surpport and mining technology which are suitable for high stress fractured ore body condition that is proposed.(5)For ore body with mined-out areas,the risk of water inrush and water recharging conditions are assessed and the mined-out areas detection technology by drilling and drainage scheme are proposed;The location,composition and shape of the lost ore in footwall are analyzed,and the quantity calculation method is given.Considering to avoid the danger of the mined-out areas,reduce the footwall loss and reducing the difficulty of the excavation and support,the safe and efficient sublevel induced caving mining scheme is proposed.(6)According to critical granular column support theory,the method that filling collapse pit with waste is used to improve the collapse angle,and then narrowed the scope of pillar.Considering the conditions of the pillar,a new method that uses magnetic pulley to discard waste rock to fill the subsidence area at any time on the surface,and shrinkage mining pillar with induced caving method with flat bottomed trench in the underground is proposed.These measures not only ensures the protection function of the pillar,also realizes the safe mining of the released pillar ore body.The techniques including forced dig?surpport and mining technology,mined-out areas detection technology by drilling,drainage scheme for mined-out area filling with water,pillar shrinkage mining technology and preparation roadway support technology have been applied in the northern mining area of Xishimen,and achieved great technical and economic effect.The production practice and theoretical analysis show that these process technologies proposed according to the three laws adaptability theory,including sublevel induced caving mining technology,can well adapt to the complex mining conditions in the northern mining area,and will help to realize safe and highly efficient mining for the fractured ore body,ore body destroyed by complex mined-out areas and pillar ore body.