METHOD FOR DEGASSING OF COAL SEAMS AND ROCK MASSES Russian patent published in 1994 - IPC

FIELD: control of state and properties of coal seams and rock masses during underground mining. SUBSTANCE: group of vibration sources are arranged in holes at seam ends normal to seam strike. Elastic vibrations within range of 60-1500 Hz are excited and weakening grouts are injected at the same time. Vibration is continued for the time for which compressive strain of seam transforms into tensile strain. Then, pulse mass hydrofrac is effected in combination with injection in seam of working fluid and vibration at frequency of working fluid injection. Subject to measurement are stress-strained state and gas concentration before, in course of, and after exposure to vibration. Used as working fluid for injection in seam is sodium hydroxide or mixture of sodium hydroxide with methanol heated up to 80 C. EFFECT: higher efficiency. 8 cl, 2 dwg