In order to carry out the underground gasification of coal, we must at first examine the relations, between movement velocity of borehole fire front and blast quantity, oxygen concentration in the blast.
According to the many observations in USSR, the increase of the concentration of oxygen in the blast and the blast guantity increase the rate of fire front movement.
The author analyzed these relations mathematically and calculated the necessary dimensions, i.e. suitable concentration of oxygen in the blast and necessary quantity of blast in case of underground gasification of coal in Japan.
And also relations between humidity of coal seam and max. temperature of borehole were examined. By these results, we will plan the most desirable underground gasification layout in Japan.