The evaluation of a deposit and mining project is a continuous process rather than a single act. Changes in budget, evaluation criteria, or in the area of costs and incomes may change results valid up to now and the views on using a deposit. Geological quantities are measurable with the help of geological conclusions and engineering calculations. Raw material reserves and their quality are defined as a substance that can be recovered with profit through current technologies and prices. This definition can result in two misunderstandings: geological reserves and the quality of raw materials are understood as variables not connected with mining activities. However, the quantity and quality of remaining reserves depends on changes in our geological knowledge, changing economic conditions, as well as on the exhaustion of reserves. The quantity of reserves and value of the cut-off grade depends not only on geological factors but also upon the methods of deposit extraction, costs and prices.
The relevance of the work. Crushed stone, crushed rock and very coarse (mostly crushed plant) soils are the most widely used in the construction of open pit haul roads. However, the strength performance of these media has been studied insufficiently, due, inter alia, to the fact that there are no reliable methods for their determination. The purpose of the work is to develop a reliable method for determining the strength performance of pre-compacted crushed stone, crushed rock and very coarse soils. Research methods. To achieve the purpose, an analysis of the design features of the existing oblique shear apparatus was carried out, elements and nodes were identified that needed refinement to ensure test media pre-compaction, a statistical analysis of the data obtained on the improved oblique shear apparatus, as well as their comparison with the results obtained by testing according to standard methods, were performed. Research results. A design of an improved oblique shear apparatus has been developed, which allows determining the strength performance of statically and dynamically pre-compacted crushed stone, crushed rock and very coarse soils. The required geometric parameters of its individual elements are determined depending on the maximum particle size of the test media, and the order of preparation for the experiment and its conduct is given. Conclusions. The proposed design of an improved oblique shear apparatus allows determining the strength performance of pre-compacted crushed stone, crushed rock and very coarse soils with a particle size of up to 20–30 mm. In order to avoid the occurrence of a keyway effect and to obtain chaotic results, the optimal clearance between the upper and lower holders should be 0.3 of the maximum particle size. To obtain the confidence interval of the measured breaking load value ±10% of the weighted average value with a confidence level of 90% when implementing the oblique shear method, taking into account possible misses, it is necessary to repeat the experiment with the same factors at least 5 times.
Annotation In the work, studies were carried out on the effect of the dimensions of rock samples and the shape of their end faces on the tensile strength limits. Sandstones, aleurolites and their interlayers were tested. The core diameter was 36-78 mm, prevailing 50-70 mm. Rocks are mainly me- dium- and fine-grained. The fracture of cores into pieces took place along thin layers of carbonaceous materials, aleurolites, cracks and cleavage, in places of accumulation and plaque of carbonaceous, carbonate and other weak substances in the form of continuous films, scattered spots and debris. All tests were carried out on the press in accordance with the recommenda- tions of the current GOST, samples were divided by applying a load along the generatrix. It was found that the tensile strength of the test samples var- ied from 0.15 to 21 MPa. The results obtained proved conclusively that cores can be used to solve production and technical problems without pre- liminary treatment of their end surfaces at the ratio of heights to diameters from 0.31 to 1.6. This will allow to increase the volume of tests of samples taken in wells by 60%, and obtain reliable information and thus more fully and reliably substantiate geomechanical conditions, Attachment and protec- tion of mine workings and optimal angles of slopes of quarry sides and ledges at open method of coal mining. This issue has been little studied and requires further research in every geological-economic region of Kuzbass.
Abstract. The specific weight of the open coal mining method in Kuzbass is constantly growing due to higher hazard and low profitability of the underground mining method. It is possible to reduce the cost of open-pit coal mining using overburden rock in constructing temporary pit roads. The purpose of the work is to justify the possibility of using overburden rock for the construction of temporary technological roads. To this end, we set the tasks to determine the rational granulometric composition of crushed rock, dependences of its unit weight, static elastic modulus, and ultimate shear resistance. This study justifies the most efficient granulometric composition of crushed rock based on theoretical studies of the optimal structure of granular materials, taking into account the probability theory of particle-particle packing, laboratory studies of the dependence of the unit weight and the static elastic modulus on the content of particles of different sizes, and also the calculation of ultimate shear resistance of crushed rocks. As a result of the conducted studies, it has been established that the optimal granulometric composition of crushed rock, which at the same time ensures high values of unit weight, static elastic modulus and ultimate shear resistance, is achieved when the content of particles larger than half of the maximum is 40 to 55% and increases integrally with decreasing of the average particle diameter.
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