The Choice of Technology and Equipment for Coal Seamsof Different Bedding Excavation at Kuzbass Surface MinesBased on Digging Capacity and Unit Costs

The paper deals with an approach to the choice of equipment and technological schemes for the extraction of coal seams of different bedding by excavators of high specific productivity. A wide variety of mining and geological conditions for the coal seams bedding in the quarry fields of Kuzbass (Western Siberia, Russia) determines the use of a variety of high-performance excavation (rope and hydraulic shovels, hydraulic backhoes, draglines) and transport (dump trucks, railway trains, draglines) equipment used in various technological schemes. The problem lies in the choice of the excavator type and the technological scheme of its use for extracting coal from seams with different dip angles and thickness within the boundaries of one quarry field in order to achieve maximum productivity and economic efficiency of the entire site development. This article substantiates the analysis of the present and promising coal mining technologies using mechanical shovels, draglines and hydraulic backhoes in order to determine the optimal technological schemes for specific conditions. The basic principle of the proposed idea is to ensure the maximum ratio of the excavator's actual performance and unit costs, taking into account geological conditions and coal loss during extraction. In this regard, based on the analysis, the article presents recommendations for choosing a technological scheme when replacing equipment based on mining and geological conditions. Under certain circumstances, the analysis may result in a recommendation for a complete replacement of the excavator fleet. The advantage of the presented method, along with computational efficiency and visualization, is the applicability for the analysis of technological schemes of any complexity, which makes it possible to use it for the design of sections that develop complex-structured coal deposit

Influence of fracture incidence angle on the local stress state of the near-slope zone of the overburden ledge

Актуальность. Напряженно-деформированное состояние массива горных пород при открытой разработке месторождений полезных ископаемых, равно как и при строительстве в грунтах выемок значительных размеров, зависит как от механических свойств пород, так и от структурно-текстурных особенностей массива горных пород. В частности, наличие трещин в приоткосной зоне уступа может значительно ослабить его устойчивость, а направление и угол падения трещин относительно откоса уступа изменяют расположение напряженных зон внутри массива относительно поверхности обнажения. Актуальной научно-практической задачей представляется выявление зон повышенных механических напряжений с целью прогноза поведения массивов горных пород с различными структурно-текстурными свойствами. Цель: выявление зон концентрации напряжений в приоткосной части уступа в массиве горных пород с различными структурно-текстурными свойствами при ведении открытых горных работ. Методы: математическое моделирование массивов горных пород с учётом их физико-механических свойств и структурно-текстурных особенностей методом конечных элементов, обработка результатов экспериментальных исследований. Результаты. Приведено описание математической модели упругого поведения естественного трещиноватого массива горных пород, имеющего поверхность обнажения в виде уступа, а также закономерности распределения концентрации напряжений в нём. Описано напряжённо-деформированное состояние нагруженного и ненагруженного массивов в ненарушенном и нарушенном трещинами различной ориентации состоянии. Описано положение зон концентрации растягивающих напряжений, проведено сравнение их значений для уступов с различным строением. Выявлены повышенные значения растягивающих напряжений в массиве при направлении падения трещин от откоса уступа по сравнению с ненарушенным состоянием и при направлении падения трещин в сторону откоса уступа.Relevance. The stress-strain state of the rock massif during open-pit mining of mineral deposits, as well as during construction in excavations of significant size, depends on both the mechanical properties of rocks and the structural and textural features of the rock massif. In particular, the presence of cracks in the near-slope zone of the ledge can significantly weaken its stability, and the direction and angle of crack incidence relative to the ledge slope change the location of stress zones within the massif relative to the surface of the outcrop. The identification of zones of increased mechanical stresses in order to predict the behavior of rock massifs with different structural-textural properties is an urgent scientific and practical task. The main aim is identification of the stress concentration zones in the near-slope part of the ledge in the rock massif with different structural-textural properties during open-pit mining. Methods: mathematical modeling of rock massifs with regard to their physical and mechanical properties and structural and textural features using the finite element method, processing the results of experimental studies. Results. The paper introduces the description of the mathematical model of the elastic behavior of a natural fractured rock massif with an outcrop surface in the form of a ledge, as well as the laws of stress concentration distribution in it. The stress-strain state of loaded and unloaded massifs in the undisturbed and disturbed by cracks of different orientation states is described, and their values for ledges with different structure are compared. The authors have revealed the increased values of tensile stresses in the massif in the direction of crack incidence from the ledge slope compared to the undisturbed state and in the direction of crack incidence toward the ledge slope