Tectonic coal is a soft coal, and the integrity of a tectonic coal seam can become compromised by the formation of cracks under the action of tectonic stresses. A series of tests were conducted to investigate the effect of the mass ratios of tectonic coal on its rock characteristics, including coal gas adsorption tests, specific surface measurements, and initial gas velocity determinations. The study showed that the adsorption value of coal sample gradually increased with increases in the mass ratio of tectonic coal. When the tectonic coal mass ratio reached 50%, the adsorption of the coal sample and initial gas velocity Delta p reached highest values. In addition, a mathematical model using the Gibbs function was developed to determine the relationship between the initial gas velocity and the different mass ratios of tectonic coal. This research provides a theoretical foundation for further research on the control of coal and gas outbursts. (C) 2020 Published by Elsevier B.V.