The Effect of Advance Boreholes on the Noise Level and Stress State in the Zone Directly Adjoining the Working Face

Abstract

Drilling horizontal and rise boreholes is recommended as a protective measure in burst-prone seams of the Central Donbass, including those at the Yunkom pit. If the rise boreholes are intersected by horizontal ones, a so-called drainage network is formed; this is employed in many seams, including the Andreevskii, Bezymyannyi, etc. At the present time, no account is taken during borehole drilling of the varying degree to which a seam is subject to rock bursts. But seismo-acoustic investigations have shown that a coal seam does not have a uniform burst hazard over its whole length; long safe zones alternate with short dangerous ones, entry to a danger zone being clearly indicated by an increase in noise [2]. Experience shows that a borehole network does not always afford adequate protection against rock bursts. In the period from July 1959 through September 1962, for example, a network of boreholes was drilled in the Andreevskii seam, but several bursts occurred during this period: seven were recorded during rise borehole drilling, one during horizontal borehole drilling, and three during mining operations in the face. Most of the bursts were small save the last one, Tolstyi seams. Since noise level is considered as a warning sign of a rock burst — the greater the noise, the greater is the danger — this shows the influence of drainage drilling on burst hazard.