Features of mine pressure development in the underground working of chromite ores of North Kazakhstan

Autor: T. M. Ermekov, V. N. Shashkin, V. A. Uskov, M. G. Abuov, A. M. Freidin
Rok vydání: 1994
Předmět:
Zdroj: Journal of Mining Science. 29:482-487
ISSN: 1573-8736
1062-7391
DOI: 10.1007/bf00733227
Popis: The main proven reserves of chromite ores of the North Kazakhstan are localized within the South Kimpersaisk rock mass of ultrabasites: three large deposits ('40 Years of Kazakhstan,' 'Diamond-Pearl,"Million'), eight medium deposits, five small and many ore developments [1]. Working of these ores which are unique in the scale of the reserves and quality is carried out by the Don Mining and Ore-Dressing Combine (DON GOK). Perspectives for development of the Combine are connected with the underground working method. Introduction of underground mining technology commenced in the 'Molodezhnaya' (40 Years of Kazakhstan deposit), and experience of working is used in newly constructed mines. The deposit within the Molodezhnaya pit is a series of gently-sloping chromite ore bodies broken up by a dense network of cracks with serpentine, talc-mica, and serpophyte fillers. The rocks surrounding the deposits are dunite serpentinites, pyroxene dunites, and harzburgites formed as a result of autometamorphism of the hyperbasite rock mass. The ore mineral is a chrome-spinellid of magnochromite composition containing chromium oxide from 38 to 40% in lean • ores and up to 54-57 % in rich ores. The main characteristics and constants of the rocks are ores are given in Table 1. The location of the deposit in the Ulytausk anticlinorium and its joining through the main Ural fault with the West-Mugadzharsk synclinorium [2, 3] causes high primary horizontal stresses in the rock mass. Determination of the magnitude and direction of principal stresses in the rock mass was carried out by BIOGEM and the Institute of Mining, Ministry of Ferrous Metallurgy of the USSR. According to measurements at level -135 m for the Molodezhnaya pit a 1 (least of compressive stresses) is 16 MPa orientated over the azimuth 341 ° having a slope of 21 ° to the horizontal plane; o- 3 (greatest of the compressive stresses) is 11 MPa orientated over the azimuth 251 ° having a slope to the horizontal plane of 43°; o-2 (intermediate) is 14 MPa perpendicular to the first two and it has a corresponding deviation from the vertical (Fig. 1). In analyzing the effect of cracking for the Molodezhnaya pit on the stability of horizontal mine workings it is estabiished that with placing of workings across the strike of the ore body (crosscuts) the most critical crack system is submeridional (its western subsystem) with an azimuth of dip 283 and an angle of dip 50 °. The structural weakening factor for the rock mass is Kwe = 0.43. Tangential stresses in the rock mass corresponding to the most critical crack system in workings of this type may be determined from the expression
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