Journal of Mining Science

The authors analyze the structure of the elasticity tensors and compliance coefficients in a special linearly elastic and transversely isotropic material with paradox behavior. The intrinsic moduli and states are found for the elasticity tensors if this material. The extreme values of Young’s modulus, shear modulus and Poisson’s ratio are determined. The characteristics of the nearest tensor of elasticity moduli are obtained.

In the current study, uniaxial compressive strength, Schmidt hammer and Sonic velocity tests are performed on NX size rock core samples from Sakesar and Namal formation limestone. Least square regression analysis is used to develop any possible correlations between the destructive and non-destructive test results. Empirical models, for predicting the uniaxial compressive strength of rocks by using the rebound number and P-wave/S-wave velocity, have been developed and evaluated. Analysis shows that the empirical model for predicting UCS with Schmidt hammer rebound number is more reliable over a wide range of strength values for both the formations. Whereas the model that uses P-wave/S-wave velocities is reliable particularly when the strength values are low to medium.

The collected data on long-runout rockslides induced be large-scale underground blasts are presented. The critical conditions of the rockslides are determined as a function of the dynamic impact, rockfall volume, as well as the slope height and gradient. It is shown that the main condition for the mobile rockslides is their volume exceeding 10⁶-10⁸ m³. A collateral effect for rockslides in case of smaller volume of 10⁶-10⁷ m³ is the presence of an acceleration phase at the slope toe and the absence of a counter slope. The relations of the avalanche front range, rockslide volume and fall height are given. It is mentioned that the avalanche range is associated with their composition, in particular, rock-and-ice or rock-and-snow avalanches feature increased mobility starting from their volumes of 10⁵ m³. A brief review of theoretical and modeling studies intended to explain the reduced friction in large avalanches is provided.

Three influences on physical modeling results of unstable dynamic displacements along fault edges under triggered relaxation are considered. The fault filler is assumed to be quartz sand placed in-between moving tiff and rough plates. This quartz sand interlayer is subject to variation in compaction, to relaxation from stresses and to a burst air flow across the interlayer to simulate gas rush in the fault. The relaxation periods in the compact sand packing under the influence of the gas flow are determined.

The current situation and development trends in the biological degasification of coal are reviewed. It is shown that methane desorption is a consequence of rock mass destruction by activity of microorganisms and releasing bacterial metabolites. The influence of microorganisms on coal as a function of a prevailing microbial community and its variety, access of oxygen and nutritious substrates is observed. Advancement of the biological method for coal field degasification based on the methanotrophy is discussed.

Layouts of reloading points in the cyclical-and-continuous technology for deep-level surface mining are analyzed. The innovative structure of a reloading point involving dump trucks drivethrough passing has been proposed; the structure will make it possible to increase reloading point productivity, cut the costs for rock mass extraction, and reduce the time of motor transport maneuvering. Dependence of general funds saving for overburden rock extraction upon the open pit depth while constructing a reloading point with the drivethrough passing comparing to a dead-end unloading of various-capacity dump trucks has been determined.

The classification of the methods available for diagnostic of mining machinery mounting groups with roller bearings is considered with indicated advantages and disadvantages. The model is constructed to describe formation of shock pulses in roller bearings when different defects are generated in them. This model is suitable for the availability monitoring of the machinery mounting groups. The applicability of wavelet transforms instead of the standard fast Fourier transform to random processes and vibro-acoustic signals is tested for the detection of defects in manufacture and operation of mining machines.

The influence of non-ionic compounds in combination with sodium oleate on the contrast behavior of flotation response of calcium minerals is investigated theoretically and experimentally. The flotation and adsorption analyses are carried out with monomineral fractions of calcite and scheelite, while the flotation process analysis is conducted with an ore material screened into size grades of -44 and -15 urn. The process conditions of the highest difference in adsorption of oleate and contrast in extraction of scheelite and calcite are found. The conditions of the maximum depression of calcite in the rougher flotation circuit are determined.

The theoretical and experimental substantiation of the behavior of ferrous sphalerite in magnetic separation is given in terms of the Gorevka deposit ore. In sphalerite of this deposit, the content of isomorphous iron ranges as 4–9%. The Móssbauer spectroscopy showed the singlet and two doublet lines of iron, demonstrating separate arrays of iron atoms in sphalerite lattice, with formation of Fe-Fe pairs and clusters of three or more iron atoms. It is found that distribution of iron in sphalerite into three forms coincides for magnetic and nonmagnetic products of zinc concentrate separation. It is determined that magnetic separation undivides sphalerite grains by the isomorphous iron content but is governed by the genetic features of the deposit formation—association of sphalerite with magnetic minerals (pyrrhotine and siderite) and the absence of such associations in galena.

The modeling procedure is developed to describe heat-exchange processes in outdoor summer storage piles of frozen coal produced in winter. This procedure takes into account thermophysical properties of coal and the pile bottom soil, pile structure, climatic factors and the presence of a heat-insulating coating over the pile. In terms of central Yakutia, it is shown that maximum transition of coal from frozen state (piling in January-March) to thawed condition at the pile height more than 5 m will make 25-35% by the end of the warm season (beginning of October). Application of simple and available heat-insulating materials can reduce thawing intensity by up to 2 times. Natural cold weakens the aggravating effect of oxidizing processes on coal quality in long-term storage of coal and its shipment to remote and hard-to-reach places.