Experimental Study On The Gas Concentration Distribution And Migration Rule In The Goaf Of Compound Mining Face

Along with the development of the modern comprehensive mechanized mining in the coal mine, the unceasingly expanding mining scale and mining acceleration, the mining destruction for the original gas occurrence balance is more apparent. The gas emission of the working face presents large quantities, high strength and unevenly characteristics, thus the treatment of the gas disaster will face new challenge than before; On the other hand, the use of comprehensive mining process and high yield and high efficiency intensive production mode, it makes the development of technologies for controlling gas could not keep up with the pace of coal production increases, and it also makes the safety production in coal mine is facing a new threat.The gas emission of mining goaf is one of the important reasons of causing the gas overrun of working face, so the study and control on goaf gas has become the main task of the gas control. This paper has studied the goaf gas concentration distribution in mining face of U-shape ventilation, Y-shape ventilation, "U+L"-shape ventilation through the method of combining theoretical analysis and experimental research, and summarized the goaf gas migration rule of different ventilation system in mining face.This paper firstly based on research work made by pioneers, analyses the rock properties of the goaf caving zone, gas main emission source and the influence of air leakage in gas emission mined-out area systematically; Analyses the migration features and the flowing mechanism of gas in mined-out in theory by introducing the concept of porous media; Introduces the flow similar conditions, the flow similarity criterion and similarity theorem to establish the similar experimental model, and analyses the application of similarity theory in the similar material experiment research of the gas migration in the goaf of mining face.The similar experimental model of many systems compound mining goaf was established by combining gas flow theory and similarity theory, the experiment of the goaf gas concentration distribution determination for U-shape ventilation, "U+L"-shape of two intakes one return, "U+L"-shape of one intakes two return, Y-shape of two intakes one return, Y-shape of one intakes one return, obtained the gas concentration distribution rule in the goaf of different ventilation system, and detailed reflects the gas concentration distribution trend along the direction and tendency towards direction in the goaf caving zone of different ventilation system through the graph.Tests the rule of the goaf gas concentration distribution of U-shape ventilation system after change into the draught wind speeds, draw a conclusion that wind speed increase would make goaf gas concentration distribution curve integral to deep direction, can reduce gas concentration of the working face to a certain extent, but after analysis found that cannot solve the upper corner gas off-gauge problems.Finally, this paper analyses the gas concentration distribution and migration rule in the goaf comparison different ventilation system, and summarizes the rule combined with the characteristics of each ventilation systems, and all above results can provide certain theoretical reference for the selection of ventilation system and the gas treatment of the compound mining face in the actual production.