Purpose. A methodology development for predicting the geomechanical situation when mining an ore deposit with steep-dipping layers, taking into account the uncertainty in determining the rock properties, which is a consequence of the rock mass heterogeneity. Methods. The assessment of the open-pit wall stability is based on a combination of numerical simulation of the rock stress-strain state (SSS) and probabilistic analysis. The finite element method is used to determine the changes in the SSS that occur at various stages of mining operations due to design changes in the overall open-pit slope angle. The elastic-plastic model of the medium and the Mohr-Coulomb failure criterion are implemented in the codes of the 3D finite element analysis program RS3 (Rocscience). Stochastic simulation is used to assess random risks associated with natural object state variations. Findings. The distribution of maximum shear strains, which localizes the real or potential sliding surfaces in the open-pit wall at various stages of ore mining, has been identified. Based on the Shear Strength Reduction procedure, the open-pit wall Strength Reduction Factor (SRF) has been determined. The probabilities of open-pit wall stability loss, as well as the decrease in the strength reduction factor below the standard level at all stages of the ore body mining, have been revealed. Originality. For the first time, for real mining-geological conditions of a deep ore open pit, the dependence of the strength reduction factor on the overall wall slope angle, which changes during mining of each steep layer, has been determined. For each stage of mining operations, for the first time, the probability of a decrease in the open-pit wall stability below the standard level has been determined based on stochastic simulation. Practical implications. The ratio between the open-pit contour characteristic (overall slope angle) and the probabilistic safety factor is the basis for practical solutions to ensure the efficiency and safety of mining at various stages of friable and hard overburden excavation, ore extraction, as well as for the subsequent optimization of the open-pit design contours.
It is generally accepted that the color and performance characteristics of liquid thermal insulation coatings are affected by the combined effect of various climatic factors such as solar radiation, temperature fluctuations, moisture, precipitation and others. This work presents the results of a scientific study of the full-scale exposure of coatings with regard to climatic ageing. Methods have been carried out, such as: spectrophotometry and direct scanning; determining adhesion, determining the adhesion strength of facing and protective coatings; and thermal conductivity and thermal resistance. As the results of the research work have shown, only in situ climatic tests, accompanied by the obligatory recording of the aggressive factors affecting the coating, make it possible to assess changes in the properties of epoxy coatings in full-scale conditions and, consequently, their climatic resistance by the methods of spectrophotometry and direct scanning. The ageing of polymer composites is known to be accompanied by a change not only in elasticity but also in color. Of the epoxy coatings tested, Etal-45M showed the greatest color variation during the in situ climate test. The most decorative resistant coatings are obtained using epoxy resin ED-20 + modified epoxy resin Etal-1440N.
Various lumping technologies of finely dispersed chromite concentrates using charge roasting processes have been considered. In this respect, it was noted that the charge formulation used in the production does not provide the required strength of the produced pellets. The authors of the article propose the use of the well-known method for the ferrosilicon calcium fluxes (FSCF) synthesis with the replacement of Callovian clays with a composition based on diatomites and industrial and waste products of the Eurasian group (ERG) enterprises in order to increase the strength of pellets and agglomerate. This method enabled us to produce roasted pellets with high strength, to ensure the optimal ratio of components, to decrease the pellet roasting temperature by 150-200°C and to increase water resistance and congelation resistance. Technological parameters can be also improved by beneficiation of the source chromite raw material, effectively used by Turkish manufacturers of chrome products. One way to increase the chrome industry raw material base of the Republic of Kazakhstan is the involvement of the “12 Geophysical Deposit” into the processing of the industrial ore. However, the produced finely dispersed chromium concentrates require lumping followed by smelting in furnaces for ferrochrome. The high silica and iron content in the host rock of chromium concentrate enables to obtain strong pellets without additional additives.
Processing industrial products and technogenic waste is an important task in the mining and metallurgical industry. In Kazakhstan, the processing of chrome ore from the Kempirsay group of deposits has produced more than 15 million tonnes of slurry tailings containing up to 30 wt% chrome oxide. The best results in the world for the processing of fine chromium raw materials are shown by Turkish enterprises with the use of the separation of slurries by size classes and beneficiation on concentration tables. The authors conducted researches for beneficiation of chrome slurry from Dubersay tailings pond (Kazakhstan) with the use of similar technological methods that enabled to obtain concentrates with chrome oxide content of 51 wt% and increasing the yield of beneficiated fine-graded chrome concentrates by 14% as compared with the existing beneficiation process. Strong chromium pellets with a crushing resistance of over 5000 N/pellet were produced from the rich chromium concentrates with the use of the ferrofluxing iron-calcium-silica binder technology by roasting the composition consisting of rich chromium concentrate, ferrous diatomite, and intermediate products and wastes of the chromium industry.
Providing safe drinking water to people in developing countries is an urgent worldwide water problem and a main issue in the UN Sustainable Development Goals. One of the most efficient and cheapest methods to attain these goals is to promote the use of slow sand filters. This review shows that slow sand filters can efficiently provide safe drinking water to people living in rural communities not served by a central water supply. Probably, the most important aspect of SSF for developing and less-developed countries is its function as a biological filter. WASH problems mainly relate to the spread of viruses, bacteria, and parasites. The surface and shallow groundwater in developing countries around urban areas and settlements are often polluted by domestic wastewater containing these microbes and nutrients. Thus, SSF’s function is to treat raw water in the form of diluted wastewater where high temperature and access to nutrients probably mean a high growth rate of microbes and algae but probably also high predation and high efficiency of the SSF. However, factors that may adversely affect the removal of microbiological constituents are mainly low temperature, high and intermittent flow rates, reduced sand depth, filter immaturity, and various filter amendments. Further research is thus needed in these areas, specifically for developing countries.
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