Assessment of failure condition of the extracted seams of the firm roof in dependence on the rock mass character

Abstract

As a result of the deposit caving, the original stress balance of the rock mass is affected; therefore, the stress always increases around the mined-out workings. The stress increase results in the stope surroundings compression distinguished by a certain surface subsidence measurable (the surface also features substantially smaller horizontal shifts as the second vector component of the general movement towards the mined-out workings metacentre). Determination of this subsidence value in relation to the extent and thickness of the mined-out workings is important to recognize the conditions under which a complete failure of the firm overlying layers occurred. At the first extraction in the area, that means failure in the whole thickness of overlying carboniferous rocks.