When ore deposits are worked by mass caving using deep holes in the presence of rock pressure manifestations, great importance attaches to the stability of the workings at the bottom of the blocks during these mass blasting operations. Technical mining literature gives no research data on the selection of the optimum parameters for the protective (buffer) slice of caved ore above the bottom of the block.* Moreover, when breaking ore out by inclined slices onto an inclined undercut or onto caved ore and rock, it is important to know the compactabllity of the caved ore.Field study of the buffering properties of caved ores and their compaction as a function of the basic parameters used for the mining-out work is extremely complicated. Laboratory research into these questions fails to provide a truly correct qualitative evaluation of the phenomena.Our aim was to study these phenomena in laboratory conditions, maintaining geometric and dynamic similartry between the mine and the model. Metal models were made from sheet iron with a wall thickness of 10 mm and size of 400 x 400 x 500 mm. Holes were bored in the bottom of the model, two of them 15 mm in diameter for clamping the model rigidly to the base (support), and two for fixing datum points and a marked-off piece The models were fixed to a rigid base (support) made from tubes with a diameter of 60 ram. The mark-off piece was a strip of sheet iron of 3 mm gauge and size 20 X 200 mm. A strip of millimerer paper was glued to the piece before each explosion. The linear value of compaction as a function of the slice thickness, of the size of the charge and of the method used to place the charge, was determined by the difference in length between the rods in the datum points before and after the explosion.These datum points consisted of metal plates of 1 mm gauge, 200 x 200 mm, which were fixed to metal rods or metal tubes of outside diameter 10 and 6 mm. The rubbing surfaces of the datum points were greased to reduce friction between the wails and the base of the tubes.We studied martite and hydrohematite-martite ores (size fractions 0-2.5, 2.5-5.0, and 5.0-7.0 mm).The hole charges consisted of sectors of fuse cord laid inside an explosive frame. Three deep-hole patterns were examined: a paraUel arrangement, a fan-shaped arrangement from a single drill stall, and a fan-shaped arrangement from two stalls. The fuse used was DSH-A. Firing was electrical, using ~D-8-56 instantaneous detonators. The link-up of the detonating network was carried out using a main conductor of the PV type. No failures or incomplete firings were recorded.Thirty-eight tests were carried out with the parallel hole cut. In ore of the 0-2.5 mm size, the thickness of the buffer layer b varies from 9.1 to 26.5 cm, and the compaction value l correspondingly from 1.0 to 5.5 cm. For a buffer layer of 9.2 cm thickness, datum point displacement (i.e., or compaction) was 1.4 cm. Where the layer thickness changed from 19.9 to 21.3 cm, the displacement value was 3.3-3.6 cm. With a further increase in the laye...

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Large-scale ore breaking by deep boreholes is usually preceded by the formation of a compensation space. The shapes and sizes of compensation spaces are often chosen without reference to the geologic bedding conditions. In practice in ore mines in the Krivoi Rog field, we often find cases in which compensation spaces differing in size as well as shape are used in practically the same geological conditions. In other words, there are at present no scientifically based recommendations for the parameters of the compensation spaces, although such recommendations are badly needed, because the shapes and sizes of the compensation spaces largely govern not only the crushing quality of the cut ore but also the economic indices of working underground districts (blocks). It is enough to say that the output per man-shift in the formation of the compensation spaces is much less than that in large-scale caving of the ore (see Table 1).We have carried out an investigation to determine the influence of the shape and size of the compensation space on the quality of crushing. The research was carried out in the laboratory, and the results were compared with the indices attained in production conditions.

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The work is aimed at determining parameters of advance borehole stoping by hydraulic monitors leading to rational use of reserves structured according to ore types at deposits by means of advance stoping with selective disintegration of high-grade martite ores. The research methods include experimental investigations of parameters of breaking a high-grade martite ore massif by high-pressure water jets of borehole monitors; laboratory studies of technological properties of hydrodisintegrated products and their concentratibility; theoretical generalization of experimental data. The research has resulted in developing experimental borehole hydraulic monitors and determining basic technical parameters of high-pressure water jets; determining regularities of hydraulic monitor disintegration of high-grade martite ores considering structural and mineralogical characteristics of the ores and hydrodisintegration modes; proving the fact that the process of high-grade martite ore disintegration by monitors is also the process of ore disintegration to the level of ore mineral grain release providing the higher quality disintegration product after subsequent dewatering than that of the initial one. The scientific novelty of the research consists in determining a criterion of hydrodisintegration of martites, conditions of forming a required fractional composition of monitor disintegration products through controlling stability of a pulse of the water jet action on the stope face. The practical relevance of the monitor breaking process in conditions of mining units at deep levels of Kryvbas underground mines consists in providing advanced stoping of rich martite ores through raises and obtaining a new kind of product – martite superconcentrate.