Efficiency of preparation of mountain mass at careers of building materials

Authors:

O. K. Ishchenko, Cand. Sc. (Tech.), orcid.org/0000-0003-2449-5258, National Mining University, Dnipro, Ukraine, e-mail:  This email address is being protected from spambots. You need JavaScript enabled to view it.

V. M. Konoval, Cand. Sc. (Tech.), Assoc. Prof., orcid.org/0000-0002-6740-6617, Cherkasy State Technological Universitу, Cherkasy, Ukraine

K. S. Ishchenko, Cand. Sc. (Tech.), Senior Research Fellow, orcid.org/0000-0003-2237-871Х, M. S. Polyakov Institute of Geotechnical Mechanics, NAS of Ukraine, Dnipro, Ukraine, е-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract:

Purpose. To conduct an assessment of the effectiveness of rock breaking in a complex array using a new design of borehole charges to develop a resource-saving and environmentally safe method of mining construction materials on non-ore quarries.

Methodology. To substantiate the rational parameters of explosive destruction of rocks with complex structural features, such as granites, in the conditions of the “Sivach” quarry, experimental studies were carried out to study the structure of the rock massif ‒ orientation of microcracks of different morphology and anisotropy of physicomechanical properties of rock-forming minerals and their spatial position on the block. The main characteristics of the fractured structure of the granite massif are studied using the method of stepler imaging of exposed faces at horizons chosen for industrial tests of an explosive rock breaking method.

Findings. Experimental studies have determined the effect of cracks on the nature of explosive destruction of an anisotropic massif. To achieve the goal, holes were drilled at along the bottom line with a diameter 43 mm to a depth of 1.0‒1.5 m and charges with a cartridged explosive material (EM) – ammonite № 6 GV – were undermined.

In terms of the dimensions of the large a and small b axes of the explosion funnel and its orientation relative to the sides of the light, the coefficient of anisotropy was calculated from the expression K = a/b, which averaged 1.14. Using the developed nomogram and taking into account the data of the anisotropy coefficient, the parameters of the well grid of the valid blast design were corrected at the experimental section of the block equal to 4.5 ´ 5.5 m instead of 5 ´ 5 m. Using the changed parameters of the blast design, mass explosions were carried out in the experimental and control sections and the results of crushing the broken rock mass with the use of the oblique-planed photographic planimetric method were estimated. The results of industrial experiments have shown that the use of modified blast design parameters using variable-charge designs reduces the diameter of the average chunk by about 30 % and the consumption of industrial explosives by 10‒40 %. The output of the conditioned piece (201‒600 mm) increases by 10 %.

Originality. The scientific novelty of the proposed explosive technology of crushing hard rocks of complex structure, realized in a new method of breaking up locally-fractured rocks involves:

- considering the identified zones of increased fracturing in the control and experimental sections the directions of local cracks and the extent of zones of increased fracturing in the block array which are oriented relative to the sides of the world were determined whose parameters were used to calculate the anisotropy coefficient;

- аccording to the anisotropy coefficient, a nomogram was constructed to correct the blast design;

- based on the changed parameters of the blast design in the holls drilled in the massif with a pronounced local fracturing, combined charges of variable cross section were formed, which made it possible to improve the results of crushing the broken rock mass.

Practical value. The presented results of industrial tests of the proposed design of a combined borehole charge implemented in the new method of destruction of strong locally fractured rocks allow for a constant charge weight to increase its length and, more evenly distribute the explosive over the height of the ledge, as a consequence. At the same time, the conditions for the transfer of explosion energy from explosive charge to destroyed array change with the formation of a different-grade and multidirectional stress field. As a result, the role of tensile and shearing stresses contributing to a more even crushing of the rocks increases.

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