Study on Minimum Sampling Depth of Coal Seam Gas Content Determination Considering Dilatancy and Softening Theory

To determine the reasonable minimum sampling depth of coal seam gas content determination, the elastic-plastic model of coal body around the tunnel considering the characteristics of dilatancy and softening was established, the expression of the minimum sampling depth of the coal seam gas content was obtained and the actual verification was carried out. The main influencing factors of determining the sampling depth were analyzed. The results show that: the main factors controlling the minimum sampling depth are the initial stress, supporting stress, coal strength, and tunnel radius. The burial depth is deeper and the coal is softer, the sampling depth should be longer; the sampling depth should increase in large section roadway and the depth of the sample should increase with the decrease of support stress.