Study On Deformation Of Narrow Pillar Of Roadway Driving Along Next Goaf Of Full Caving Face And Its Control In Deep Coal Mine

Coal is the main energy resource of our country. With the continuous mining of coal, the coal resources of the shallow area become less and less, and now the focus is transferred to deep coal seam mining. In order to promote the coal recovery of fully mechanized caving, many domestic researchers proposed a new method which is driving roadway along next goaf with narrow coal pillar. The deformation of narrow coal pillar is complex because of the influence of dynamic pressure, which brings great challenge for the bolt support technology of coal roadway. The research conducted in this paper has very important significance for reducing the loss of coal and the costs of supporting and maintaining of roadway, promoting the economic benefit and ensuring the safe production.In this paper, supported by Weijiadi Coal Mine of Jingyuan Coal Industry Group of Gansu Province, with laboratory test, field test, theoretical analysis and numerical simulation, the mechanical characteristics, deformation, damification of coal under dynamic pressure, optimum coal pillar size and the supporting method are studied systemicly, which is aimed at providing theoretical base for optimum coal pillar size of coal pillar and its supporting designing.With the research of caving behavior of the overburden on the roadway along next goaf of fully mechanized caving mining face, the main roof will break liake "O-X". Based on the theory of key block, the characteristical parameters of the key block are studied. A logical analysis model is built, the stability of the overburden on the roadway along next goaf of fully mechanized caving mining face before drilling, drilling and after drilling is analyzed.With the synthesized analyse of the mechanical state and deformation of the coal pillar of the roadway along next goaf of fully mechanized caving mining face, the edge of the coal along next goaf are divided by unloading relax area, plastic strengthening area, elastic deformation area and in situ stress area, and the formulation of the stress and the width of yielding zone of the coal pillar is deduced. The narrow pillar is located at the supporting stress decreased area of the maginal coal mass and the yielding area of the coal mass along next goaf. With the influence of the driving of the roadway along next goaf, the narrow pillar will deform again. The deformation of the coal pillar can be decreased by strengthening support, and the stability of the coal pillar can be maintained.With the study of the deformation of the surrounding rock of the roadway driving along next goaf and the principle of the interaction of bolt and surrounding rock, it is discovered that, the narrow coal pillar has low strength and small bearing capacity because of the influence of the side abutment pressure of the upper curtate. With the mining influence of current mining face, the narrow pillar will deformed and the supporting pressure will be transferred to the coal mass side, and the deformation of the coal mass side increases and it is very hard to control. So, it is very important to improve the stability of the narrow coal pillar. The basic principle of the control of narrow coal pillar is proposed.FLAC3D is used in this chapter to do the numerical study of the roadway of X1-107 mining face at Weijiadi Coal Mine. The ground pressure and the bolt support effect of the roadway of the mining face are obtained, and the width of coal pillar, the support kind and support parameter are determined.The monitoring of the stability and the bolt condition of air roadway and conveyor roadway of X1-107 mining face at Weijiadi Coal Mine is conducted. The engineering practice shows that narrow coal pillar is the key to the stability of roadway alone next goaf. The strengthening of the narrow coal pillar support can improve the bearing capability of cal pillar, decrease the rotary settlement of the triangular block, control the settlement of the roof coal, maintain the stability of coal pillar itself, decrease the relative convergence of the sides of roadway and ensure the whole stability of the surrounding rock of the roadway. The air roadway and conveyor roadway of X1-107 mining face are supported by high strength thread steel bolt and enhanced with small diameter prestressed anchor cable on the roof, which has maintain the stability of the surrounding rock effectively.