The gas extraction radius by boreholes is mainly related to the factors such as the coal-seam gas content,the air permeability coefficient,the diameter and negative pressure of gas extraction borehole,the gas extraction purpose,time and so on.A certain results can be obtained for the coal seam having better permeability and pressure measuring condition with the traditional determination method for gas extraction radius,but its efficiency is rather low;when the coal seam has poor permeability,the success rate of the measurement is extremely low and its applicability is poor.For this reason,direct measuring method was used for the measurement of dynamic gas extraction flow from boreholes on the basis of the coal-seam gas content being known,the extraction rate was determined according to the extraction purpose,and then the extraction radius by the borehole at different extraction time was also determined.The practice indicated that this method is practical and easy to generalize.

With the increase of mining depth,the stress field in mining faces changes from shallow to deep part,obvious change occurred in distribution regularity of the prediction index for the heading face in bulky seam under the condition of high strata stress,so the urgent need is to understand the distribution regularity of the stress field in the heading face in extra-soft seam with high strata stress.The distribution regularity of the stress field in front of the heading face in the extra-soft seam with high strata stress was obtained with a combined method of theoretical analysis,field survey and numerical analysis.Test research was made on the sensitive index and critical value for outburst prediction in the heading face in the extra-soft seam with high strata stress and high gas pressure in Xinzhuangzi Mine in Huainan Coal Mining area.