Large-scale blasting-down in stripping the Tyrnyauz mineral deposit

Abstract

The Tyrnyauz tungsten-molybdenum deposit in the mountains of the central Caucasus has hitherto been worked by underground mining. However, progress in open-cut mining with up-to-date machinery has enabled us to convert to the more economic combined (open-underground) method of working.The first open-cut operations were begun in 1969, directly above the working underground blocks in the Mukulansk are field of the deposit. Experience accumulated by the group showed the possibility of further extension of the open-cut workings. Combined open-underground working enables us to extract a large amount of ore which would be lost in underground mining because it would be economically disadvantageous to extract it. Furthermore, the use of the combined method enables us to advance the opening up of new veins and to increase the output per man-shift.However, combined mining in conjunction with the complex relief of the region requires the solution of some very complicated technical problems -the disposition and retention of a large volume of caved rock in a steeply dipping gorge, the elimination of a large landslide in the western part of the quarry boundary, the cutting of motor roads in rocky mountain territory, etc. The most complex of these problems is the elimination of the landslide. The moving mass of rock with f = 12-14, and area of about 1 km 2, and a bulk of 10-12 million m a, slides about 100 cm per year and presents a real threat to the further development of dumping operations in the quarry. There are technical difficulties in eliminating it by the usual method (explosion of loosening charges in boreholes and excavation from above downward), owing to the danger of running an excavator on the fissured slope in the zone of active movement of the rocks and because of the lack of reliable approaches to the moving mass.Under these conditions, the only possible method is to knock down the moving mass by large-scale blasting using charges which are approached from underground workings cut in stable zones of the rock not affected by the movement.In 1972 the Tyrnyauz Combine, in conjunction with the Soyuzvzryvprom Trust, decided to use large-scale blasting to eliminate the landslide.The whole of the sliding mass lies within the take of theproposed Mukulanskii quarry, and therefore all the costs of blasting must be assigned to the estimates of the open-cut operations in the Mukulansk ore body, and thus they do not influence the initial estimated costs of the open-cut workings.A plan for the first large-scale blast to knock down the slide, 4-5 million m 3 in volume, was devised by the Central Production-Experimental Special Construction Laboratory of the Soyuzvzryvprom Trust in conjunction with the Tyrnyauz Combine. The main outlines of the plan are as follows.The slide region is at an elevation of 2690-3087 m above sea level and includes three beds of rock extending in the north-south direction along the strike of the Kurgashilli-Tau ridge and sloping steeply down to the thalweg of the Bol'shaya Mukulanskaya gorge. The mo...