Kononenko M. Geomechanical substantiation of underground infrastructure parameters during iron-ore mining with the application of emulsion explosives

The dissertation is dedicated to the solution of the actual scientific-and-practical issue of geomechanical substantiation of the underground infrastructure parameters during the iron-ore mining with the application of emulsion explosives based on the established patterns of crushing zones formation, intensive crumpling and cracking around the charging cavity, which are formed in the rock mass under the action of the explosion, and as well as establishing patterns of changes in the density and detonation velocity of emulsion explosives along the length of the formed column of charge at different angles of inclination of the boreholes. The analytical models of the crushing zones radius, intensive crumpling and cracking formed in the rock mass around the charging cavity under explosive loading have been developed for the first time, which comprehensively taking into account the diameter of the charging cavity, the detonation characteristics of the explosive substance, the strength of the rocks, as well as their cracking and compaction under the action of rock pressure and explosion, as well as the diameter of the explosive charge. The finite-element analysis of the destruction of model mass around the charging cavity under the action of the explosion energy established the power dependence of the change in the radius of the crumpling zones, intensive grinding and cracking on the diameter of the charging cavity, the detonation characteristics of the explosive substance, and the tensile-compressive strength limit of the rocks. The suitability of the analytical models for determining the radius of the specified zones was established by comparing the results of the research of the mathematical models of the radius of these zones with the results of numerical modeling for the boundary conditions of a monolithic non-cracked mass. The power-law dependence of the change in the line of least resistance on the diameter of the charging cavity, the density and detonation velocity of the explosive substance, and the limit of tensile-compressive strength of rocks was obtained by modeling the process of formation of the ejection funnel with application of the finite element method based on the main tensile stress of the model. Further research revealed the most accurate formula for calculating the line of least resistance, which is an analytical dependence on the zone of intensive grinding. The methodology for calculating the redistribution of the density of the emulsion explosive in charging cavities with different angles of inclination has been developed. The power dependence of the change in the density of the bulk emulsion explosive Ukrainit-PP-2 along the length of the formed charge column up to 55 m, depending on its initial density and the angle of inclination of the borehole from 0 to 90º has been established. The power dependence of the change in the detonation velocity of the bulk emulsion explosive Ukrainit-PP-2 on the charge diameter and density have been performed by using the rheostat method and established by natural experiments. The rational initial density of the emulsion explosive Ukrainit-PP-2 was determined with taking into account these dependencies, which varies within the range of 800-1000 kg/cu.m and at the same time the uniform detonation velocity is maintained along the length of the charge column up to 35 m at different angles of inclination of the boreholes. The resulting dependencies became the basis for the development and implementation of the software product “Density and Velocity of Detonation”, which allows you to calculate the density and velocity of detonation along the formed charge column for bulk emulsion explosive Ukrainit-PP-2 in both ascending and descending boreholes with different angles of their inclination. Also, taking into account these dependencies made it possible to develop a methodology for calculating the performance factor based on the degree of realization of the detonation velocity for all industrial explosives, which allows comprehensive consideration of the heat and volume of explosion gases, their density and detonation velocity.