Outburst-dangerous rocks

OUTBURST-DANGEROUS ROCKS (EN: ejected rock, thrown-out rock, rock liable to outburst; DE: ausbruchgefahrliche Gesteine; FR: roches à degagements instantanes; ES: rocas eruptivas; RU: выбросоопасные породы) are the places within the massifs of the rock, which are dangerous because of the sudden outbursts.

The outburst danger is determined within the limits of the geological-industrial region, or within the limits of the underground mine field, according to the data of the exploratory drilling. The degree of this indicator is determined during the process of the conducting of the mine workings, according to the quantity of the discs within the 1 metre of the core samples, which have been obtained during the drilling of the boreholes with the diameter of 59-76 millimetres. According to this indicator, and also according to the peculiarities and quantity of the gas, which has been released, they distinguish the zones with the high, medium, and low degree of the danger. In case of the penetration of the mine workings, using the drilling-blasting method, they prevent the outbursts of the rock and gas, on the account of the unloading slots, and of the barrier bulkheads, in combination with the optimization of the drilling-blasting works, and there are introduced the mechanized methods for the penetration without the explosions.

The optimization of the parameters for the drilling-blasting works within the outburst-dangerous rocks is based on the change of the schemes for the positioning of the blastholes, on the change of the procedure for the detonation of the charges, and also on the usage of the special cartridges with the explosive substances. The length of the blastholes is 1.6-1.8 metres. They adopt as the norm for the calculation of the charges for the blastholes the quantity from 1.2 to 1.5 kilograms of the safety explosive substances per 1 cubic metre of the rock, which is destructed. They perform the detonation of the complete set of the charges during 2-3 stages. If the mine working is conducted simultaneously through the layers of the outburst-dangerous rocks, and through the layers of the rocks, which are not dangerous because of the outburst, and at the same time the outburst-dangerous layer is situated within the lower or middle part of the stope, then they drill the kerf blastholes through this layer; when this layer is located within the upper part of the stope within the mine working, then there is advised the detonation of the charges within the blastholes, which are situated only within the lower part of the stope. Within the zones with the high degree of the danger, for the decreasing of the dynamic impact onto the massif, there is advised the usage of the cartridges with the explosive substances with the damping interlayers. For the directed destruction of the outburst-dangerous rocks, they use the charges with the aerial cavity within the bottom part of the blasthole. The usage of the special technology for the drilling-blasting works permits to decrease by 2-3 times the intensity of the outbursts, and to increase by 1.5-2 times the speed for the conducting of the mine workings.

In case of the method for the penetration without the explosions, the major equipment is the penetrating complexes, and the combined cutting-loading machines of the rotary type (the forecast of the outburst danger is performed using the acoustic method). The major parameters of the process are regulated. Thus, the speed for the conducting of the mine workings through the rocks with the high degree of the danger must not exceed 0.5 metres per hour, and with the average degree of the danger, the speed must not exceed 1 metre per hour; the shape of the stope is hemispherical, with the depth of the hemisphere of 0.2-0.3 of the diameter of the mine working. For the fixation within the rocks with the coefficient of the strength f > 10 at the depth of up to 1200 metres, they use the lightweight linings of the types of the sprayed concrete, or of the anchors with the mesh. The major technical-economic indicators, in case of the method for the conducting of the mine workings within the outburst-dangerous rocks, with the usage of the combined cutting-loading machines, are by 4-5 times higher, than in case of the drilling-blasting method; there are excluded the outbursts of the rock and gas, and there are practically completely mechanized the processes for the excavation of the rock, and for the fixation of the mine workings.