Home – Home – Jornals – Journal of Mining Sciences 2020 number 1

A new method is proposed for predicting rock pressure, including static, kinematic and dynamic approaches. The static approach calculates strain state using the known classical method based on the mining guidelines. The kinematic approach takes into account the own weight of overlying strata and makes the kinematic approach more specific. Dynamics is traced as nonlinear deformation in the course of mining, and the dynamic approach needs additional in-situ information on the rock mass behavior. The three approaches provide the total displacement of roof rocks in a stope. The authors discuss a quasi-static approach determining dynamics in terms of the pliability of rocks ahead of an advancing face and feasibility of obtaining experimental data for the new method implementation.

The article considers the problem on compression of an isotropic medium with a variable width slot with cohesive zones at the ends. Under the action of tectonic and gravitational forces in rock mass, contact zones appear between the slot surfaces. The author analyzes the case of a number of the contact zones between the slot surfaces. In a part of the contact zone, cohesion of the slot edges takes place, while sliding is possible in the other part. The unknown parameters of the partial closure of the slot are found by solving a system of singular integro-differential equations. The contact stresses, the cohesion forces, as well as the sizes of the contact areas, cohesion zones and pre-fracture end zones are determined.

Based on the analysis, generalization and statistical processing of experimental data, the guideline values are determined for the physical and mechanical properties of loamy soil for construction of earthfill dams at liquid mining waste storages. A close parabolic relationship is found between the cohesion, internal friction angle and natural moisture content of soil. The authors present the method of real-time prediction of earthfill dam parameters with regard to spatial variability of soil strength.

The theoretical model is proposed, which allows tracing continuation of seismic vibrations after cessation of blast effect by the analysis of velocigrams recording on ground surface during underground explosions. The comparison of the model and experimental velocigrams of massive blasts shows validity of elliptical filters for second-order low frequencies in modeling waveforms of the velocigrams. The model efficiency in the detection of time-delay errors is proved. The conditions of predicting peak particle velocities based on explosive weight per blast are determined. The pre-conditions for the resonance excitation in the rock mass-guarded object system are discussed, and the blast-induced load is predicted.

A physical model is created to describe stage-by-stage fracture of rock mass by deep-hole blasting. The analytical dependences are presented for main parameters of massive blasting. The zones of intensive and passive fragmentation are identified in a blasted bench. The formulas are obtained to calculate volumes of different size particles in these zones. The automated determination procedure of particle size distribution is proposed. The program in Microsoft Visual Studio 2017 environment allows the automated analysis of blasthole pattern in a bench and particle size distribution in broken rock mass depending on initial data.

Uniformity index n represents the range of fragment size distribution and it is applied to evaluate fragment size by Rosin and Rammler cumulative distribution function for a muck pile. The uniformity index n of fragment size distributionhas been assessed by digital image analysis technique for several blasthole parameters and different zones of in-situ rock mass conditions in five mines having a wide range of blastabilty index. The uniformity index n of the Rosin and Rammler equation has been determined by a new procedure using curve fitting program with the best correlation for all groups of results. The obtained real values of n had significant differences with estimated n by the former equations. Relations between n and several blasthole parameters, blastabilty index and mean fragment size (X₅₀) of the results and their various combinations have been analyzed. Finally, a new empirical model having a good correlation has been developed to predict n value.

Some of the coal mines use dragline for the overburden removal of coal top as its geometric, since the initial cost is high with low running cost. Most of the draglines operating in Indian mines have conventional analog control under Ward-Leonard method. To improve the efficiency of those, to reduce the power consumption and to provide maintenance-less operation in the electrical system, the microprocessor-based digital control system is proposed to replace the analog method of control. This paper analyzes and presents a case study of real time performance of one upgraded digitally controlled Ward-Leonard dragline, operating in an Indian mine-field. It shows the improvement in specific energy consumption and suggests maintenance issues based on the comparative study of breakdown status before and after the upgradation.

The aim of this study is to investigate the applicability of artificial neural networks (ANN) and game theory in the development of an underground mining method selection model. To realize this, six different ANN models which can evaluate geometric and rock mass properties of underground mine, environmental factors and ventilation conditions to determine mining methods that satisfy the safety conditions for an underground mine were developed. Among the mining methods determined by ANNs, the optimal mining method was determined by the ultimatum game, in which a compromise between safety and economy conditions was simulated. By using a combination of developed ANN models and ultimatum game, a new model based on artificial neural networks and game theory for the selection of underground mining method was developed. This model can make predictions in the presence of lack of information by following technological developments and new findings obtained in scientific/sectoral studies if learning is continuous. Moreover, the model can evaluate all selection criteria and provide literature-based solutions. In the light of findings obtained within this study, it is revealed that artificial neural networks and game theory can be used in the selection of underground mining methods.

In mid-May 2014, flooding caused by unprecedented rainfall wreaked havoc on Serbia. In the night between May 14 and 15, the swollen Kolubara River with its tributaries flooded the Tamnava West Field and Veliki Crljeni coal open-pit mines. The paper describes the course of flood events, the consequences of the outflow of about 214.4 million m³ of water into the depressions of the open-pit mines, and the damage resulting from this devastating accident that hit the Kolubara Mining Basin.

Realization of good returns in the mining venture needs careful planning, scheduling, design and optimisation of all mining activities which are dependent upon reliable resource estimates. The mineral resource estimation method employed in a deposit thus plays a major role in reduction of risks associated in mining. Indicator kriging, ordinary kriging and inverse distance weighting methods are compared for Monywa K and L deposits. Correlation coefficients in the regression analysis of downhole composites compared with the ordinary kriging estimates for K and L deposits were 0.982 and 0.985 respectively, thus selecting it as the best estimator for the two deposits.

The authors present an efficient modification method of X-ray fluorescence separation with mineral and organic luminophores used to adjust spectral and kinetic characteristics of anomalously luminescent diamonds. The mechanism of attachment of luminophores at diamonds and hydrophobic minerals is proved, including interaction between the organic component of emulsions and the hydrophobic surface of a treated object and the concentration of insoluble luminophore grains at the organic and water interface. Selective attachment of the luminophore-bearing organic phase of emulsion at the diamond surface is achieved owing to phosphatic dispersing agents. Tri-sodium phosphate and sodium hexametaphosphate added to emulsion reduce attachment of the luminosphore-bearing organic phase at the surface of kimberlite minerals. It is shown that phosphate concentration of 1.0-1.5 g/l modifies and stabilizes spectral and kinematic parameters of kimberlite mineral on the level of initial values. This mode maintains the spectral and kinematic characteristics of anomalously luminescent diamonds at the wanted level to ensure extraction of diamonds to concentrate.

The authors prove connection between the surface activity relative to gas-liquid interface and collecting ability in flotation for derivatives of xanthogenates (xanthogenates of heavy metals). It is shown that at nonstoichiometric ration of xanthogenate and metallic salt concentrations, colloid particles are formed in solution. The influence of deviation from the nonstoichiometric ratio of xanthogenate and metallic salt concentration on the spreading velocity of the colloid system over water surface and on the collecting activity of the system is studied. It is found that the spreading velocity of derivatives of xanthigenates over water surface and their collecting activity depends on the duration of aging of the colloid system.

The experimental results on operation of electrodynamic separator with pulsed traveling magnetic field in treatment of sand mixtures with metal particles - 0.25 mm.

Part of large-scale industrial test results of milling fineness influence on lead, copper and zinc minerals flotation results in the Rudnik flotation plant are shown in this paper. Based on industrial research it has been concluded that one-stage milling and two-stage classification of complex Pb-Zn-Cu ore leads to so-called “differential milling”. Namely, galena has much faster comminution than other minerals present in ore due to galena softness. This occurrence leads to galena converting into a small particles size fractions which have low flotation rate and, at the same time, copper and zinc minerals stay “unliberated” in coarse particle size fractions (minerals are not free of mutual bonds). In this paper, recorded copper minerals flotation products results are shown, including lead underflow (copper flotation input), copper concentrate and copper underflow, in function of particle size; particle size distribution, minerals and metals distribution in function of particle size were determined; obtained research results confirmed “differential milling” assumption, as well as severe floatability difference between chalcopyrite of a different particle size.

The particle size distribution and the material constitution of samples taken from old milltailings of sulfide and oxidized ore are studied. It is shown that more than 50% of gold occurs in fine size grade of - 0.044 mm. The method of gas adsorption reveals large specific area in the samples, which is important for re-entrainment and migration of gold and associate components. It is found that gold correlates with iron-bearing species, which is useful for the magnetic separation of gold. The differential scanning calorimetry shows that the samples of the milltailings lack significant quantity of carbon black capable to adsorb gold. It is found that it is possible to generate insoluble residuum of iron cyanoferrates in the tailings, and microne size particles of mobile gold will self-settle on them.

The article presents studies into the microwave treatment effect on higher recovery of noble metals from rebellious carbonic ore. The rate of refractoriness of carbonic concentrates was determined using a package of thermal testing techniques. Bitumen is an additional criterion of the refractoriness rate of mineral dressing products. The influence of treatment time on heating of a sample is studied at different microwave capacities. The process of heating of dry concentrates in electrolytic solution is analyzed. The applicability of microwave treatment of flotation concentrates toward higher recovery of gold from rebellious carbonic ore is proved.

The author studied the process of copper removal from underspoil water at Blyavinskoe and Safyanovskoe copper ore deposits by cementation by iron. The influence of pH, consumption of cementation agent impurity ions Fe³⁺, Al³⁺ and Ca²⁺, as well as timing on the cementation performance was analyzed. The mechanism of the process was determined, and by-reactions resulting in over-consumption of cementation agent were revealed. The studies of the material constitution of cemented copper showed that the concentrate quality worsened because of the joint settling of basic aluminum and calcium sulfates. The obtained results make it possible to draw the conclusion on applicability of cementation for removal of copper from underspoil water.

The authors have analyzed relative earth heat infiltration in artificial ground freezing in the context of formation of frozen wall in mine shafts. The artificial ground freezing modeling reveals considerable dependence of the earth heat infiltration on the thermal properties of ground, process variables of freezing plant and time. The earth heat infiltration comes to a steady-state value 5-8 months after beginning of freezing. The formula is obtained for estimation of the steady-state value for the relative earth heat infiltration at different temperatures of ground and freezing brine.