Study On Gas Migration Law And Extraction Technology Of Upper-level Seam Mining In Goaf

Gas disaster is one of the most serious disasters that affect the safe and efficient mining of coal mine,which will cause significant economic losses and a large number of casualties.When the goaf gas emission to the coal mining face,gas accumulation is easy to occur,and the upper corner of the return air is the most prone position to gas overrun.The mining face of Yuecheng coal mine adopts the method of slicing mining,and the unloading bottom coal will release a large amount of gas,which brings new challenges to gas disaster control.In order to ensure the safe mining of Yuecheng coal mining face,"large aperture high drilling" were used to extract gas of the goaf,according to the occurrence characteristics of coal seam,mine ventilation,gas emission characteristics and so on.In this paper,taking the 1309(upper)working face as the engineering background,the movement law of overlying strata,the stress state and the plastic failure zone of the stope floor,the gas migration law in goaf were studied by using the methods of theoretical analysis,theoretical calculation,field test and numerical simulation.Based on the gas source of the working face,the gas emission characteristics of the working face were analyzed and the gas emission prediction of the working face was carried out by using the method of different-source prediction.Then,this paper researched the evolution characteristics and spatial distribution characteristics of the roof mining fracture field,the stress state and deformation failure characteristics of the coal seam floor were analyzed,and the range and depth of plastic failure zone of the bottom coal seam in stope was calculated.And then,this paper analyzed the characteristics of the diffusion,floating and accumulation of the pressure relief gas,and analyzed the coupling law of the mining fracture field and gas flow.After that,the paper studied the gas migration law in goaf under "U" ventilation and extracting gas by Fluent numerical simulation.Finally,based on the analysis of the commonly used gas drainage methods in goaf and the engineering background,this paper put forward the technology of gas drainage with "large aperture high drilling".The height of the "three zones" of the overlying strata in the mining area was calculated by empirical formula and field test,and the height of the "large aperture high drilling" was determined,and the technical parameters of "large aperture high drilling" were designed to provide technical support for solving the gas overrun of the mining face and the upper corner of the return air.The results show that:In the working face of slicing mining,it is easier to form the gas overrun in the working face and the upper corner because of the large amount of gas emission of the unloading bottom coal seam in the mining process.The scheme of "large aperture high drilling" in Yuecheng coal mine can effectively control the gas overrun of working face and upper corner.