Study On The Law Of Roof Broken And Instability And The Control Of Large Mining Height Fully Mechanized Mining In Thick Coal Seam

The stope of thick seam fully mechanized high mining has large mining spaceand a wide range of caving rock movement.The face has the problem of rib spallingoccurrenced easily and high rate of stent stability accidents and stent crushed ordamaged, which affect the high caving face safe and efficient production severely.Therefore, it has important practical significance and the theoretical value that studyof the rule of overlying rock breaking and structural characteristics, the relationshipand control technology between the stent and the surrounding rock in thick seam fullymechanized high mining face for thick seam fully mechanized high mining achievedsafe and efficient production in our country.Similar material simulation and numerical one have applied to study of overlyingrock breaking rules and structure characteristics in fully mechanized high mining face.The research shows that with the face advancing, compared with ordinary miningheight face, fully mechanized high mining gob space is large, as well as theimmediate roof collapse in trouble when filled gob. Overlying immediate roof existedwith the form of combination cantilever, which transmitted the force of the overlyingstrata to face stent. With the collapse height increases, caving gangue gradually fillsthe goaf space and then plays on the supporting role of the overburden broken block.But this moment as the caving gangue is in the initial compression phase that thedensity is relatively low and compressible is relatively large and amount of roof spaceallowed to sink exceeded amount of broken roof block between ultimate extrusionallows subsidence. So the blocks unable to form a rock hinged beam structure, andexisted with the form of non-hinged rock beam structure, which roles in the cavinggangue and upper the lower combination of cantilever structure. After overburdencollapse to a certain height, the amount of compression of goaf caving gangue tends tolimit, and allowing sinking below the overburden ultimate the amount of rotationsubsidence. The extrusion pressure of breaking blocks is relatively large and formedarticulated beam structure. Therefore, the structure form of fully mechanized highmining face overlying strata is a combination of cantilever-Non-hinged rock beam-hinged rock beam.Based the supporting role of fully mechanized high mining gob caving gangue tooverlying rock roof instability significantly enhanced control and deflectioncharacteristics of the roof itself, the introduction of support coefficient of goaf gangueto characterize the support ability of goaf caving gangue to the overlying rock roof, and the range of overlying rock fracture of fully mechanized high mining stope andthe size of regional structure were analyzed. The formulas of roof initial and periodicbreaking step under the effect of goaf caving gangue were deduced by theoreticalanalysis. Get the roof breaking step depends on not only its own roof lithology,thickness and load conditions, but also related to the gob gangue support coefficient,and with the increase in the gangue support coefficient while increasing. While thegangue support factor was influenced by coal mining height, and meet logarithmicfunction relationship between the two. The greater the height of the mining, thesmaller gangue supporting coefficient is. The formula of traditional roof caving heightwere fixed, derived the factor of roof caving height including coal mining height, theamount of ultimate deflection of roof tiered and the residual expansion coefficient ofgoaf gangue. The method for determining overlying rock roof each regional lengthand height was gave theoretically.According to the stress state of overlying rock structures of fully mechanizedhigh mining face, the stent and overlying rock interaction mechanical model wasestablished, with the structural stability and its influencing factors are analyzed, givesthe formula of the face stent support resistance. Combined with the mining conditionsof fully mechanized high mining face and the method of identification overlying rockregional dimension in Jinhuagong coal mine of Datong mining area, the size of theface stent resistance was determined. Because of fully mechanized high mining facefeatured that the mining height is large that the the deflection space of covered rockroof generated increases that the angle of the roof allowed rotation increases, so thehinged roof structure prone to generate rotary deformation instability. From roofcontrol point of view, measures should be taken to reduce the subsidence thatoverburden hinged roof allowed, and improve the support coefficient of goaf cavinggangue, and alleviate the pressure behavior of working face.With fully mechanized high mining practice of Jinhuagong12#coal seam as theengineering background, the combination of methods of field measurement andtheoretical applied, the reason of intense pressure behavior in8218fully mechanizedhigh mining face were analyzed, which was mainly due to stent selectionunreasonable and support resistance can not meet the needs of the roof support. Basedon the above findings, the roof control technology of ahead of the pre-split blastingproposed and implemented in8210fully mechanized high mining face and it hadachieved good roof control effect in field application which ensured the face safe and efficient mining.In this paper, concerning the research results of the rule of overlying rockbreaking and structural characteristics, the relationship and control technologybetween the stent and the surrounding rock, enriched the theory and technology ofthick seam mining, and provided a theoretical basis of thick seam large mining heightto achieve safe and efficient production in our country.