Abstract: In this paper, to find out the mechanism of coal seam water injection to the gas diffusion, according to the exiting experimental conditions, the effect of moisture content of coal samples to the initial velocity of gas diffusion was taken as the breakthrough point for our research. Through the experiment, the initial velocities of gas diffusion of the coal samples with different metamorphic degrees in different moisture situations were studied. The experiment results show that the logarithmic relationship is existed bwtween the initial velocity of coal gas diffusion and the moisture content, and the initial velocity of gas diffusion is alleviated due to the water content in coal sample. In addition, the higher the metamorphic degree of coal sample is, the bigger influence of the moisture is. Moreover, it has the biggest influence when the moisture of coal sample is around 2%-7%, and when the moisture of coal sample is over 10%, the increasing of moisture content has smaller and smaller influence to the initial velocity of coal sample.

Key words: water injection coal, desorption, hole, initial velocity of gas diffusion, moisture content