Home – Home – Jornals – Journal of Mining Sciences 2013 number 3

The authors present energy estimations of mechanical-and-electromagnetic transformation of rock specimens during failure that can be of use to diagnosing rockburst hazard rate in underground mines.

The zonal disintegration is studied from a viewpoint of the spatial strain localization, a prospective idea to tackle the problem. The three-dimensional loading and unloading models are modeled numerically based on a strain-softening heterogeneous constitutive model. In the loading model, after a cylindrical tunnel is excavated, the displacement-controlled loading is conducted in the direction of the tunnel axis. However, in the unloading model, after the model has reached a static equilibrium state, a cylindrical tunnel is excavated step by step. In loading and unloading conditions, numerical results reveal that the zonal disintegration phenomenon that annular regions with high shear strains are isolated or divided by those with lower shear strains is existent. Compared with results in the loading model, results in the unloading model are even consistent with the field observations. At a plane orthogonal to the tunnel axis, the regions with higher shear strains, far away from the tunnel surface, are formed by propagation of shear bands that do not originate from the plan.

The deep rock masses are considered as granular materials containing uniform distribution of defects. Defects in the deep rock masses are characterized by the damage variable. The damage variable of the deep rock masses is determined using Mori–Tanaka’s method and Sidoroff’s method, which consider the interaction among microcracks. Effect of the pre-existing microcracks and secondary microcracks on scalar curvature and the free energy density is investigated. A new non-Euclidean mode is established, considering effect of the pre-existing microcracks and secondary microcracks. Contributions of pre-existing microcracks and secondary microcracks to the self-equilibrated stresses are derived from the free energy and the deformation incompatibilty condition. The stress fields of the surrounding rock masses around a deep circular tunnel are determined from a new non-Euclidean model.

The article describes procedure of solving inverse problems on identification of flat specimen failure by tension using in situ displacements and acoustic emission. Weak coherence area is defined by concentration of pores and modeled by a mathematical cut with lengthwise averaged normal tensile stresses. In places with high concentration of pores, Young’s modulus is “degraded,” i.e. deformation intensifies here and causes shear stresses. The latter are calculated by successive approximations of solutions of direct problems on specimen contour displacements and concentrated acoustic emission. In principle, under consideration are primal inverse problems of the continuum mechanics coupled with the new class of inverse problems on failure.

The authors discuss experimental nano-indentation results obtained on carnallite, spathic salt and sylvinite grains on Dimension ICON scanning probe microscope, as well as comparative assessments of elasticity modulus and hardness of the minerals.

The options of electrical tomography in studying complex-structure geological profiles in coal deposits are examined using mathematical modeling of electrical fields in nonuniform media. The modeling results show regular patterns of electrical fields distribution, which are used to interpret in situ data to build background models aimed at defining shape, size, occurrence conditions and physical properties of mineral deposits in weak-differentiated media. The study is illustrated by experimental research conducted on a lignite coal field.

The article discusses and extends the known concept on block structure of geomedium by Peive–Sadovsky. It is shown that interaction of structural geoblocks generates force moment. This allowed construction of rotation model of geomedium, assumption of the existence of “rotation” waves and explanation of rheidity properties of geomedium. It appears that representative values of “rotation” waves are close to the velocity values of pendulum waves (µ-waves by Oparin).

The authors have found relationship between stress state and surface roughness of main fracture in rocks: with growth of maximum normal stress in the area of fracture, surface roughness of the maximum normal stress site decreases. Based on the found relationship, the authors propose a method of estimating stress state of a material by value of the material fracture surface roughness.

Under analysis is travel of P-waves in an elastic pipe partly buried in soil with dry friction. The mathematical formulation of the problem on impact pipe driving in soil is based on the model of axial vibration of an elastic bar, considering lateral resistance described using the law of solid dry friction. The author solves problems on axial load on pipe in interaction with external elastic medium, and compares the analytical and numerical results obtained with and without accounting for the external medium deformabilit.

Aimed to improve capacity of vibro-percussion driving of steel pipes in soil, the authors describe experimental modeling of the process with additional vibration exciters of axial and transverse vibrations series-linked to impulsive load source. Workability of combination of two extended action spectrum percussion units as the vibration exciter is illustrated.

The authors study work process of pneumatic percussion units with valveless air distribution under exhaust back pressure in drilled solid removal in long horizontal hole drilling machines. It is shown that range of efficient values of the machine performance equal to maximum percussion force does not change under increase in the exhaust back pressure.

The mathematical model of positive-displacement two-way hydropercussion system includes characteristics of the system design features and their interaction with rock mass. The author analyzes numerically their influence on dynamics and integral output capability of limit cycles.

The authors show three methods of energy saving in mine ventilation: recirculating airing, minimization of main mine fan pressure by privative adjustment, and two-parameter optimization of fan performance (by rotary velocity and angle of blades). Energy conservation in using any of the methods is proved in calculations.

The presented geoinformation system is based on cloud service classification of natural and mining-induced seismic events. The data entropy-based models treat seismic signals as functions of a “waveguide” led from the seismic source to the seismic station. The quality similarity or distinction of the models is related with the genesis of seismic events. The service includes Google App Engine cloud calculating technologies, IRIS Data Management Center web-services and local seismic monitoring databases. The application of the cloud service to classifying unknown-genesis seismic events is illustrated by the examples.

Using X-ray photoelectron spectroscopy, the authors analyze the change in the surface layer composition and chemical state of atoms of chalcopyrite and sphalerite as a result of treatment by high-power nanosecond electromagnetic impulses. General regular patterns and distinctions of modification of the mineral surface and flotability under energy impulse treatment are found. The research findings are supported by the results of experimental improvement gained in selective separation of sulfides after high-power nanosecond electromagnetic treatment.

The article considers principles of constructing kinetic models of a sorptive collector layer forming at sulfide mineral surface and explains the physics of the models that consists in the connection between ions of flotation slurry liquid phase and relative fractions of mineral grain surface .

Parameters of heterogeneous machining media in magnetic-gravity, gravity and flotation machines are studied using methods of computational fluid dynamics. Numerical modeling of separation processes allowed graphical and numerical characterization of separation. The article bases suggestions on improved designs of the gravity and magnetic-gravity processing equipment and offers approach to evaluating surface energy of mineral particles in flotation modeling.

Based on analyzed redistribution of nonferrous and precious metals in aqueous and weak acid solutions passed through copper–nickel ore dressing refuses, the authors have obtained distribution of the metals in mineral phases for different levels of filtering layer in the tailings and for different contact solutions. Potential extractability of gold and platinum at 28.4 and 3.9% of the total quantity of mine refuse, respectively, using weak acid contact solution is shown in the article.