The mechanism of cracks propagation and coalescence of neighboring cracks existing in precracked rock like cylindrical specimens has been studied experimentally and numerically by considering multiple cracks in the middle part of each specimen. The pre-cracked cylindrical specimens of rock like materials are experimentally tested under uniaxial compression in a rock mechanics laboratory. Then these experiments are numerically simulated by a modified higher order displacement discontinuity method (HODDM) using cubic displacement discontinuity elements and three special crack tip elements for crack tip behavior to increase the accuracy of the Mode I and Mode II stress intensity factors (SIFs) obtained based on linear elastic fracture mechanics (LEFM) theory. The crack propagation and coalescence paths of the internal inclined crack are estimated by implementing a suitable iteration algorithm of incremental crack length extension in a direction predicted by using the maximum tangential stress criterion. The numerical and experimental results are compared showing the validity, applicability and accuracy of the present work. Finally, a numerical simulation has been accomplished to study the effect of interaction among neighboring cracks on the SIFs.
Fully mechanized backfilling mining technology with waste, fly ash, and loess, etc. provides advantages of safety and high efficiency to the extraction of coal under buildings, railways and water bodies. In this paper, the bulk ratios of backfilling bodies with different waste and fly ash mixture ratio was analyzed with MTS815.02 electro-hydraulic servo rock mechanical testing system and compacting device, the optimal mixture ratio of waste and fly ash was determined, and it proposed that the backfilling body should be firstly compacted after being backfilled into the goaf. With numerical simulation, the impacts of bulk ratio of waste and fly ash backfilling body to overlying strata movement law and surface subsidence controlling in backfilling mining were analyzed, and it figured out the bulk ratio of backfilling body that could ensure a reasonable range of surface subsidence. Finally, the engineering application confirmed that the strata movement controlling in fully mechanized backfilling mining was more effective, the surface buildings and facilities were not severely influenced. The above achievements could provide technical reference for the successful implementation of fully mechanized backfilling mining.
Conventional approaches to estimating reserves, optimizing mine planning, and production forecasting result in single, and often biased, forecasts. This is largely due to the non-linear propagation of errors in understanding orebodies throughout the chain of mining. A new mine planning paradigm is considered herein, integrating two elements: stochastic simulation and stochastic optimization. These elements provide an extended mathematical framework that allows modeling and direct integration of orebody uncertainty to mine design, production planning, and valuation of mining projects and operations. This stochastic framework increases the value of production schedules by 25%. Case studies also show that stochastic optimal pit limits (i) can be about 15% larger in terms of total tonnage when compared to the conventional optimal pit limits, while (ii) adding about 10% of net present value to that reported above for stochastic production scheduling within the conventionally optimal pit limits. Results suggest a potential new contribution to the sustainable utilization of natural resources.
In focus of the article is minimization of aftereffects of the large-scale accident connected with the flooding of Berezniki Potash Mine in the Perm Krai. The authors construct a synthesized geomechanical model of the flooded mine to show the mining conditions, the process of salt rock dissolution and the elastoplastic behavior of deformation and failure of undermined rock mass in time. Approaches to analyzing intensity of degeneration of load-bearing elements of the open stoping system as a consequence of salt rock dissolving are proposed. The obtained estimates are the parametric framework for prediction of the ground surface deformation using 3D mathematical modeling. The geomechanical calculation results are used in the managerial decision-making on safety of the industrial and civil infrastructure within the hazardous territory.
The article reports the results obtained in the trial of elements of the monitoring system for potentially hazardous areas at Korobkovo deposit of the Kursk Magnetic Anomaly. The system is based on the seismic and deformation measurements aimed to estimate and control shear stiffness of potentially hazardous faults. The fault shear stiffness is estimated through the analysis of parameters of seismic waves in the vicinity of a fault. The sources of seismic signals in the trial were explosions carried out at the neighbor surface and underground mines.
Different modes of advance of a pipe with a soil plug under rectangular impulse are investigated numerically and analytically with regard to dry friction between the pipe and plug and between the pipe and external stationary medium. The two model solutions are compared with and without regard to the pipe and plug elasticity. It is shown that elasticity of the pipe and plug is neglectable in case of a long-duration impulse.
The article summarizes the results of the long-term research on the anthropomorphic soil in reclaimed and successive areas of the Most Basin in Czech Republic. The main attention is paid to the main dump localities of the Most Basin monitored on the long-term basis. Based on the evaluation of the paedological development of the areas, the presence of contaminants and the development of the vegetation cover, the authors of the article propose optimal management methodology for the areas damaged by mining based on the detailed survey of individual localities within the Most Basin conditions. Emphasis is placed on the methodology of establishing areas left to undergo natural succession.
Under numerical investigation is propagation of surface pendulum waves in 3D block medium. The medium is modeled by 3D lattice of masses connected with elastic springs and viscous dampers. The surface vertical pulsed concentrated loading is considered. The displacements and velocities of the surface masses are calculated. The numerical results obtained for the block medium are compared with the similar data on elastic medium and in situ experiments carried out by other researchers.
The object of the numerical study is the travel of pendulum waves in a blocky medium under nonstationary impact of deep-seated charge blasting on the surface of the expansion chamber. The blocky model is simulated by a two-dimensional lattice of masses connected by elastic springs along the axes and diagonals. The displacements and velocities of the masses at different half-space points are calculated using the finite-difference method.
Abstract—Stationary-state combustion of fine dispersed dust–gas–air mixtures in underground workings is considered. Under the assumption that the single source of heat emission is the carbon oxidation reaction, the second-order nonlinear differential equation is obtained for the determination of temperature and the initial conditions are formulated. The analysis of the solution shows that there exist critical values of the dust–gas–air mixture flow velocity, and the excess over these critical values may result in the mixture combustion. The cross-section of mine working is related with the temperature reached in this cross section.
The authors analyze collecting capacity of desorbable species of xanthates. Desorbable species of the reagent are understood as the species capable to transfer from a mineral particle to air bubble, i.e. to gas–liquid interface, at the moment of rupture of an interlayer between these interacting objects. Flotation process performance is evaluated at the presence of a mixed coating resulting from physical and chemical adsorption and in the presence of a chemisorption coating only. The rates of spreading products of interaction between butyl ethyl xanthates and lead nitrate over water surface are found. The spreading rates and collecting capacities of the mentioned reagents are correlated. It is found that an increase in the length of the hydrocarbon fragment increases collecting capacity of a reagent and the rate of spreading of its products on water surface.
The authors study the influence of physicochemical parameters on methane adsorption capacity of coal and offer the analytical method for the methane adsorption capacity for three-phased condition of methane. It is found that in the depth interval to 300 m below surface, methane adsorption capacity measured in lab can exceed natural gas content of coal obtained from geological exploration data by 30%, and the change in the thermodynamic condition of coal–methane system brings irreversible physicochemical consequences in terms of the altered ratios of physical states of the main components. There is no linear connection between natural gas content of a coal bed and its methane adsorption capacity with respect to occurrence depth. The application of Big Data in treatment and interpretation of large data flows is described. The theoretical data predicted using the proposed method and the experimental data on methane content of Kuzbass coal agree.
Tunneling operations in urban areas are always associated with surface and subsurface ground movement, which may affect the stability of nearby structures and utilities. One of the main issues in the analysis and design of tunnels, is ground movement after the support systems and settlement systems caused by excavation. This paper takes the discrete element calculation software of Universal Distinct Element Code (UDEC) to set three dimensional calculations models to simulate the construction of Esfahan subway tunnel, analyzing the displacement and stress dynamic response during the construction process. The paper also carries out the comparison analysis of the field measurement of the ground movement. The result indicates that the simulation objectively reflected the rules of movement during the construction process. The results show that the tunnels are stable before support system installation and the tunnel induced movement is allowable.
Under consideration is the influence of various crushing techniques on the particle-size distribution and selectivity of dissociation of basic mineral components in the composition of Dalnegorsk complex ore under pretreatment. Distribution of basic elements per size grades is determined in crushing feed and in products of magnetic separation and flotation. Conditions of preparation and separation of disintegration products are described. The authors illustrate the change in the dissociation selectivity criterion in jaw crushing and in disintegration in a press to prepare different-size ore for processing by magnetic separation and flotation.
The article presents a procedure to select loading and transportation machines for an open pit complex ore mine. The choice of a shovel–dump truck production system is validated using a statistical testing method (Monte Carlo technique). Stop-watch readings allowed relating the productivity of the production system, degree of ore fragmentation and content of oversizes; the soundness of the choice of the production system based on the revealed criterion was proved. Using the law of the Palm flows, the authors determine the number and sequence of dump trucks for loading in a one-server system.
The undertaken research is aimed to reveal optimal physicochemical conditions for deep conversion of calcium-bearing alumosilicate raw material. An innovative technology of integrated extraction of nano-dispersion amorphous silica, alumina, calcium fluoride and other useful elements has been developed.
The authors solve the problem on forces required to change drilling path of air hammers in soil. Soil mass is assumed a rigid–plastic medium with the Mohr–Coulomb yield, and the air hammer deviator is considered as a nondeformable body. The problem is solved in two stages: introduction of the deviator in soil and travel of the air hammer in soil with the rear deviated at a certain angle. The loads applied to the rear, the forces and the moment required to changing the path of an air hammer in soil are calculated.
The authors discuss application of the modern concept on rock mass structure as a hierarchy of blocks and the phenomenological basis of the pendulum wave theory in the context of source areas of destructive events in natural and nature-and-production systems. The phenomenological relationship is set between Zhurkov's concentration criterion of fracture, experimental criterion of underground excavation "collapse," canonical structure of spectrum of pendulum waves by Oparin and the long-range action of heavy explosion impacts in geomedia by Sadovsky-Adushkin. The article validates the energy approach to describing transformation of elastic energy of destructive event source areas into kinetic energy of structural elements of these areas. The authors introduce a new notion of "interference seismic emission events.".
The influence of structural characteristics and interaction parameters of minerals on separation method of lead-bearing complex ore in Russia is analyzed. Based on the studies of deep dissociation of minerals under disintegration using Mineral Liberation Analyzer (MLA), the quantitative distribution of mineral associations in grain-size categories is determined. From the data on mineral dissociation, the series of mineral associations, characteristic of complex ore from some deposits, are defined using milled samples of ore material. It is shown that galena associations with chalcopyrite, fahlore, secondary copper sulphides, sphalerite, pyrite and gangue mostly occur in finely dispersed aggregates with fahlore and, to a lesser degree, with other sulphides. The obtained series of mineral associations make it possible to determine the sequence of dissociation and separation of final-size minerals in the inter-cycle operations during flotation. The primary flotation concentrate contains fahlore, secondary copper sulphides, gold associations, galena and corroded pyrite.
Intersector models are efficient mathematical and modeling tools, which are well studied and widely used in economy. It is contradictory that intersector analysis is neglected in mining, especially since no other field has accepted and implemented the application of the model of operation research as mining did. There are not many satisfactory explanations as to why this is so. In order to explain this dilemma, this paper is directed at the peculiarities and characteristics of the intersector analysis, towards observation of its application in the mining industry on the intersector model of the Mining basin of Kolubara, which operates in the system of the Electric Power Industry of Serbia, and demonstrates the implementation and validation of observations and conclusions.