Distribution Of Gas And Oxygen Concentration Field In The Goaf Of "Y+ High Pumping Alley" Working Face And Its Applications In Disaster Prevention

In recent years,the ventilation mode of “Y+ High Pumping Alley” has been widely used because of its superior gas control effect.Y-type ventilation has significant effect in solving gas accumulation in upper corner and reducing gas concentration in return air flow.High extraction roadway can reduce gas emission from goaf to working face and avoid gas exceeding limit.But “Y+ High Pumping Alley” ventilation brings more complicated air leakage in goaf,which increases the risk of spontaneous combustion of coal left over from goaf.If there is high concentration of gas in goaf,there may be a compound disaster of spontaneous combustion of coal left behind and detonation of gas.The above-mentioned goaf disasters need a suitable concentration range of gas environment,so it is very important to study the distribution law of gas concentration in goaf of “Y+ High Pumping Alley” ventilation system working face,and to optimize the ventilation extraction parameters which affect the distribution law of gas for safe mining of coal mine.The bundle pipe is laid in the goaf to monitor the change of gas concentration in the goaf during the working face moving.The gas concentration of each component was measured by gas chromatograph,and the variation rule of gas composition in goaf with the advance of working face was obtained.The dangerous zone of “spontaneous combustion” in goaf and gas compound disaster caused by residual coal were quantitatively divided by interpolation analysis.According to the similarity theory,combined with the actual situation in the field,a three-dimensional flow field test bench in the goaf was built according to a certain proportion.The flow field in goaf under the ventilation mode of “Y+ High Pumping Alley” was simulated by flow field test bench,and the distribution law of gas concentration and flow field pressure in goaf under different layout of high extraction roadway and negative pressure was studied.The influence of different layout and extraction parameters on gas concentration and flow field in porous medium of goaf is studied.The reasonable layout of high extraction roadway which can reduce air leakage and efficiently extract gas from goaf under the ventilation condition of “Y+ High Pumping Alley” is determined.At the same time,in order to effectively control gas and reduce air leakage intensity in goaf,the influence of high extraction roadway on spontaneous combustion in goaf is minimized.By changing the negative pressure of high pumping Alley in flow field test bench,the influence of negative pressure on the air volume,mixing volume and gas concentration of gob-side entry was studied,and the relationship between them was determined,and the reasonable extraction parameters of high extraction roadway were explored.In this paper,the formation conditions,judging principles and methods of compound hazard hazards caused by residual coal and gas in goaf are analyzed.COMSOL numerical simulation was used to study the gas concentration field in goaf with Y+ High Pumping Alley ventilation mode.The gas concentration field distribution map in goaf was obtained by changing the air volume of working face.The influence of different air supply on the distribution of oxygen and gas in goaf with “Y+ High Pumping Alley” ventilation mode was studied.With the increase of air volume,the boundary of the “spontaneous combustion” three-zone oxidation heating zone develops to the deep part of the goaf and its area expands;with the increase of air volume,the gas concentration in the goaf adjacent to the working face decreases significantly,and the high concentration gas transfers to the deep part of the goaf.By superimposing the gas concentration field in the floor of goaf which meets the conditions of occurrence of compound disasters,the dangerous areas of gas compound disasters caused by residual coal explosion are divided.It is concluded that there is a positive correlation between the area of composite disasters and air volume.One of the key factors to prevent and control the combined disasters of gas and coal spontaneous combustion is to reduce the air volume of working face.In this paper,based on the actual situation and measured data,using the method of similar simulation experiment and numerical simulation,the variation law of gas concentration distribution in goaf is studied,and the hazard zones are determined and classified on the basis of the research background of W1310 fully mechanized mining face in Gaohe Coal Mine.It is of great significance to study the reasonable air volume and space layout of high extraction roadway adapted to “Y+ High Pumping Alley” fully mechanized top coal caving face in preventing goaf disasters.