Coal and gas outburst analogous test under the different diameter of exposed coal seam surface

In order to study how the variation in the diameter of exposed coal seam during uncovering coal may influence coal and gas outburst properties,a coal and gas outburst analogous test device was developed to simulate coal and gas outburst,under the conditions of the different diameter of exposed coal seam surface.The experimental results show that the exposed area of coal seam has some effect on coal and gas outburst.It is displayed mainly in the following aspects: the larger the exposed area,the more easily the outburst occurs during the rock cross-cut coal uncovering,so it is possible to control outbursts by decreasing the exposed area during coal uncovering.The gas emission in coal failures is also effected by the exposed diameter,and this will change the trend of gas pressure gradient.The smaller the exposed area,the longer the coal and gas outburst lasts,the slower the gas pressure in coal seam,and less obviously the crushing capacity of gas.Under the smaller exposed area,the authors observed the smaller coal and gas outburst intensity and the lower variable quantity of temperature.The results also indicate that the size of exposed area affects the instability,destruction and throw-out characteristics of gas-containing coal.