Home – Home – Jornals – Journal of Mining Sciences 2016 number 6

It is experimentally found that shut-in pressure conforms with the fracture initiation pressure if fracture surfaces are uniformly loaded by fluid. The article shows that equaling minimal stress and shut-in pressure in local fractures results in overestimates. The error depends on the length of a hydrofracturing facility and is high under low compression in rocks (5-10 MPa). The authors put forward decisions aimed at improvement of accuracy and enhancement of information content of hydraulic fracturing in the in situ stress measurement.

The authors discuss capabilities of taking information on mechanical processes in geomaterials under post-limiting elastic deformation based on variation in IR radiation intensity. Experimental results on recording of heat emission from specimens of rock salt exposed to cyclic loading by uniaxial compression are reported. It is concluded that thermomechanical effects are useful in recording of onset of failure activation in geomaterials under cyclic loading.

The article describes physical simulation and mathematical modeling of influence exerted by injection of thermogel on configuration of water flow in water flood recovery. Recovery of oil, especially viscous oil, with such method features unstable displacement front and formation of water fingers that eventually turn into a net of water channels directed toward the lowest flow coefficient between wells. Most of oil remains immobile and is in dynamic equilibrium with the displacement water flow. The authors show that injection of thermogel in a reservoir between wells expands displacement front at the late stage of mining, which allows enhancement of oil recovery factor.

The authors describe operation of a laser deformograph within the integrated geodynamic monitoring system in Streltsov Ore Field. Capabilities and design features of the deformograph are discussed. The article demonstrates feasibility of highly accurate measurements of deformation field parameters in an operating mine. Specificity of natural oscillations of the Earth is defined, and deformation of rock mass depending on energy of a destruction source is evaluated.

Considering features of wave pre-destruction (microfailure) of rocks under blasting, the authors put forward a new investigation approach with the use of relations of dynamic elastic stress distribution in rocks and theory of cracks. The obtained relation to estimate pre-destruction zone size in relatively solid rocks under confined explosion involves pressure of gases in explosion chamber, rock pressure, crack resistance of rocks, characteristic dimension of natural jointing (presence of defects) and deformation characteristics of rocks. It is shown that dimension of pre-destruction zone in rocks depends both on natural and production factors and can differ by a few times.

A model of a continuum with a structure described by infinite order equations of motion is proposed. In case that a wave is very long as compared with the size of the structure, equations are reduced to the fourth-order equations. A closed equation of motion, including nonlinear, dispersed and wave members, is derived. It is shown that solutions in the form of soliton waves exist only in media where wave velocity grows with pressure. In the media, where soliton waves do not exist, quasi-stationary solutions with multiple frequencies prevail. It is found that the nonlinear effect of multiple frequencies is unexpectedly high even for small deformation as dispersion violently intensifies nonlinear events. Moreover, in the domain of small deformation, there exist solutions for longitudinal and transversal waves with the same length and different frequencies. The solutions for the same length waves with different frequencies most often occur in seismology and seismic explorations.

The factors that have significant influence on efficiency of rotary-percussion rock drilling with downhole machines are discussed. The results obtained in physical simulation of dynamic driving of rock-breaking indenters in rocks are reported. The results are analyzed from the standpoint of the phenomenon of alternating response of rocks to dynamic impacts.

The article presents a procedure to calculate hydraulic pressure losses in hole drilling with units equipped with replaceable core receivers and using non-Newtonian mud fluids. It is found that main hydraulic loss takes place when mud fluid flows in clearing between a drill string and drill hole walls. Numerical modeling has shown that it is possible to reduce hydraulic pressure loss by 76.5-89.0% by increasing drill string diameter by 2 mm. Based on the analytical research results, diamond drill bits and underreamers with the outer diameters of 78.0 and 78.4 mm, respectively, are manufactured for drilling operations in Talnakh ore field.

Authors review key approaches to designing small-size air drill hammers. The approach to increasing impact capacity of air drill hammers by means of buildup of blow frequency is substantiated. The experimentally obtained and compared characteristics of air drill hammers equipped with the heads made of steel and titanium prove feasibility of increasing impact capacity by means of using low density materials. The technology of thermal treatment of a titanium-alloy hammer head is described, and its laboratory testing results are reported.

This paper presents the methods and test results of the dynamic resistance of chock and rockbolt support used in Poland. By the dynamic resistance of the support is meant the ability to absorb and suppress the fast changing with time load with the value frequently exceeding the working support capacity of the supports. This feature is required when using the support in excavations endangered by rock mass tremors, especially such tremors, which can result in rockbursts. Based on the carried out studies and analyses, numerical values of loads are given that cause the slide of a friction prop, bending the support sections, loss of stability of dog heading support and load-carrying ability of bolts.

The analysis of methods to account for stripping time difference at the stage of determination of limits in deep open pit mining reveals advantages and shortcomings of the methods and provides a principled approach to determination of a discount ultimate stripping ratio for the most representative geological and geotechnical conditions of diamond-bearing ore bodies in the form of single pipes. Discounting of ultimate stripping ratios is based on adding the common formula with an average mean discount coefficient represented by a correlation of mining rate decrease, stripping zone height and highwall slope angle. It is shown that target variation of the factors included in the discount ultimate stripping ratio allows considerable influence on depth and efficiency of open pit mining.

The author characterizes ore production loss depending on time, properties and production technology. Typification of technologies aimed at improvement of ore-drawing quality using canopies is performed. Operating principle of canopies is theoretically generalized, and recommendations on using canopies are made. It is proved that separation of abandoned ore from overlying rocks under canopies during ore-drawing improves mineral production quality.

The article describes the applied research findings on selecting a resource-saving technology to ensure drastic reduction in loss of high-grade Kyshtym quartz. The economical-mathematical modeling yields relationships between mine efficiency, ground conditions, mine design and technology factors, and the optimal variant of a combination mining technology is determined using the maximum profit criterion. Full-scale physical simulation of closed-spaced charge blasting effect on reduction in overgrinding of quartz is discussed. Drilling and blasting pattern for experimental breaking of quartz by explosions is determined.

Using Hammett indicators, X-ray fluorescence spectroscopy and atomic force microscopy, the authors analyze influence of high-voltage nanosecond impulses on structure and chemistry of surface and on process properties of calcium-bearing minerals. As a result of impulse energy inputs for t ≤ 30 s, the change in the structure and functions of mineral surface includes: enhancement of electron-donor capacity and formation of structural defects on the surface of fluorite, and enhancement of acceptor capacity of the surface of calcite and scheelite. Pre-treatment of mono-mineral samples by electrical impulses increases flotation ability of calcium-bearing minerals: increment in froth recovery makes 10–12% for scheelite, 5–6% for fluorite and 7–8% for calcite.

New information is obtained on composition and properties of a bio-reagent-oxidizer generated by mesophilic aerobic chemo-tropholytic bacteria Acidithiobaccilus ferrooxidans under oxidation of iron ions (II) in sulfuric acid solution. The composition and properties of the bio-reagent are compared with iron sulfate (III) used to intensify agitation and heap leaching of metals from sulfide ores and concentrates. The research with IR spectroscopy, mass spectrometry, Moessbauer spectrometry and potentiometry has revealed distinctive features of the bio-reagent and explained the experimentally observed increase in its oxidative activity when interacting with mine.

The article presents data of experimental studies into magnetic properties of iron-bearing sulfide and nonsulfide minerals under radiation and heating. It is found that bulk magnetic susceptibility has increased more than 100 times in pyrite and by 6 times in bauxite ore. Usefulness of radiation-and-heating magnetization in modification and processing of bauxite and tin-bearing minerals is demonstrated.

The article presents data on separation of minerals of eudialyte ore with low magnetic susceptibility using a high-intensity wet magnetic separator and pulp pulsation. The optimal separator variables of the magnetic field inductance, pulp pulsation and matrix filler diameter to ensure maximum efficiency of processing are determined.

The discussed challenge and its prospects in mining geoinformation science are connected with Big Data concept-flows of large sets of various data on mining. The authors describe Big Data technology and its general implementation on mini-clusters using Hadoop and MapReduce with case studies presented.

The presented system is intended for multistage hydraulic fracturing in long open holes of any orientation to create transversal fractures with a radius to 5 m in soft and medium-hard rocks. The downhole system has an inbuilt transport unit. This fracking equipment uses chemically active fluids generated in the fractured interval by mixture of two components injected in individual high-pressure hoses.

The method is based on transcapillary penetration of fluorescent fluid (EpoDye colorant) in the finest cavities and flaws on the surface of polished sections. Luminophor-filed voids become visible under UV light and optical microscope. The voids are estimated with respect to their kinds, sizes and area. The estimates and the statistical property of void distribution are described.