| Most of the mines in our country have the characteristics of fire and gas coexisting,so one of the key work in disaster prevention of underground mine is preventing collaborative fire and gas in the goaf of fully mechanized caving face,along with the wide application of combined mining technology in coal mine site.According to numerical calculation,experimental analysis and field test,the fracture evolution process of stope’s overlying rock,three-dimensional model of stope,stage characteristics of the coal spontaneous combustion,characteristics of gas explosion in the goaf,collaborative preventing of gas and fire in the goaf are studied in the paper,at the same time the actual application in the site was tested and analyzed.Based on the working face 011604 of Gong Wu Su mine,with the help of simulation software,the embedded of different horizon in the model was lined,the overburden movement law under different push degrees,the destruction law of overburden and the distribution law of overburden stress in the coal seam were studied.The results revealed the evolution process of the overlying rock in the stope with the evolution process of working face.Through monitoring and analyzing overburden subsidence under different push degrees,the height of the stope caving zone and fractured zone was determined.The figure about sinking displacement of stope showed that crack development was trapezoidal on the trend and tendency.Through the developmental research of elastic and plastic zone in the process of mining areas,the destruction law of overburden was analyzed from the space and time.Through the research of compressive tensile stress in the process of mining areas,the fracture evolution process of stope’s overlying rock was analyzed from the stress point.Based on the numerical calculation software naming UDEC,the caving process of the deformation,abscission layer and instability was analyzed.The test values and simulation values were compared and analyzed.According to numerical calculation,theoretical analysis and field test,the model size of three-dimensional trapezoidal structure was comprehensively determined.The result showed that the caving zone’s height of overlying rock was 15 meters,the height of fractured zone was 46 meters,the upper width of working face towards the fractured zone was 34.6 meters,the upper width of open-off cut towards the fractured zone was 33.8 meters,the upper width of working face leaning to the fractured zone was 24.5 meters,the fracture angle of open-off cut was 62 degrees,the fracture angle of working face was 58 degrees,the fracture angle of the intake and return air state was 62 degrees.In the heating experiment of the coal spontaneous combustion,the law of gaseous product in the different temperature rising phase was researched through selecting multiple coal sample in the mine.According to the characteristics of the experimental coal sample,the prediction index system of the coal spontaneous combustion was determined.The critical oxygen concentration indictor of the coal spontaneous combustion was 7 percent according to gaseous product of the coal samples under the different oxygen concentration and thermodynamics characteristics of the oxidation.With the help of the numerical calculation software of the gas explosion,the influence of gas explosion was analyzed from the gaseous product under the different phase of the coal spontaneous combustion.It included the change of the explosion pressure,temperature,intermediate product and the key reaction steps.The results showed that the associated gas in the slow oxidation phase inhibited gas explosion,the associated gas in the accelerating oxidation phase promoted gas explosion,and that the associated gas in the intense oxidation phase promoted gas explosion.The inhibitory effect on gas explosion between CO2 and N2 were compared and analyzed under the three phases in the process of coal spontaneous combustion.It suggested the inhibitory effect of CO2 on gas explosion was more obvious.The paper analyzed the flow of gas in the goaf according to the seepage flow mechanics of porous media.The three-dimensional trapezoidal stope structure was selected as the model.Based on the Fluent,the gas migration and the distribution of the oxygen concentration was simulated under the different ventilation ways in the three-dimensional stope.The three-dimensional stope included U,U+L,U+L+gas injection.It put forward the ways of collaborative preventing about gas transfinite and coal spontaneous combustion of the goaf.For example the working face 011604 of Gong Wu Su mine,inerting explosion suppression scheme injecting CO2 was put forward according to the research results in the paper.The change of the maximum width in the spontaneous combustion oxidation zone under different injection volume was curving fitting.In accordance with the relevant provisions,they were determined that the maximum width,recovery rate,dead time and the dynamic equilibrium relationship between the shortest spontaneous combustion periods of coal in the spontaneous combustion oxidation zone.It determined parameter of carbon dioxide injection against fire in gob from the point of theory.The monitoring data of field showed that the influence of scheme for the prevention of goaf spontaneous combustion was positive. |
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