ABSTRACT
Rockbursts are mainly encountered in ore, coal, and potash mines, also in tunnels or caverns in hard competent rock like granite or quartzite. Every rockburst is accompanied by a loud report and a ground tremor - a seismic shock - the strength of which varies with the strength of the burst. The rockbursts in coal mines are violent failures of the coal seam, causing ejection of broken coal and often taking the form of an abrupt movement of the face or sidewall. The majority of rockbursts are less severe yet still involve a hazard to personnel. When a similar disintegration of coal is associated with considerable emission of gas, the event might be taken for a gas-coal-outburst. The appearance of rockbursts depends largely on local conditions. Sudden floor heave is relatively often involved if there are underlying coal beds. Soft layers between the seam and the main roof are liable to break down.
