Home – Home – Jornals – Fundamental and applied issues of mining 2019 number 1

This study presents tests of samples with discontinuity made of artificial geomaterial (concrete-sand mixture) having triangular profile of surface roughness under shear loading with the boundary “constant normal stiffness” condition, with three values of normal compressive load: 0.5, 0.9, and 1.2 MPa. The patterns of deformation were determined at each stage of loading diagrams: linear, nonlinear, peak load and residual strength. The empirical dependences of the ultimate shear stress on normal stress were constructed for different values of roughness.

For initially anisotropic media, a theory of plasticity based on the multiplicity of eigenvalues is constructed. If the eigenvalues are simple, then the condition of plasticity of such medium is a parallelepiped, and the position on the edge of the parallelepiped is called the state of complete plasticity, the position on the face is called the state of incomplete plasticity. To illustrate these states, the problem of forcing down a rigid wedge into the initial anisotropic medium with the condition of plasticity in the form of a parallelepiped is solved. The limit load and the maximum penetration depth with a given initial speed of the striker are determined.

For the media with periodic changes in Young's modulus and yield strength, the problems of stress, strain and displacement distribution around single excavations of spherical and cylindrical shape are solved. Block structure of the medium is determined by the difference between the elastic modules and the yield strength in the blocks and interblock space. In each case analytical solutions are obtained. The influence of blocks quantity, difference in block properties and interlayers on the nature of changes in stresses, strains and displacements was studied. It is noted that block structure is one of the factors for forming zonal disintegration around excavations.

For the design of deepening of the Sarbaisky and Yuzhno-Sarbaisky quarries and involvement of new deposits into development, a detailed study of the geomechanical conditions of ore mining was required. In order to clarify the geomechanical model of the Sarbaisky quarry, the stress-strain state of the rocks was evaluated. The stresses in the adjacent rock mass were monitored using the Kaiser effect in rocks during loading of the borehole walls with a Goodman hydraulic jack. For the Yuzhno-Sarbaisky quarry, mathematical modeling by the finite element method in three-dimensional formulation was carried out.

The paper examines a possible relationship of the occurrence of catastrophic situations (earthquakes, rock bursts, etc.) in unordinary conditions and manifestations of tectonic processes in the bowels of the Earth at the “lower crust-upper mantle” level. It is shown that such tectonics is observed in basite-ultrabasite xenoliths bearing clear features of deep-seated deformation (olivine twinning, curved crystals, drag grains of spinel, preferred orientation of optical indicatrices of minerals, etc.). The mentioned relationship is studied from the viewpoint of relaxation reaction of rock masses, rocks and their element components on mass displacements in the Earth’s depths.

The features are investigated and a design diagram is developed for radial cracks propagation in a layered rock mass during blasting of borehole charges and hydraulic fracturing. To calculate the stress state of an elastic rock mass with cracks, we used the boundary element method in a three-dimensional formulation. As a result of these calculations, the influence of the strength properties of rock mass layers on the shape of radial cracks and their area was determined

Triple gain of the maximum amplitudes or massif vibrations in a final phase of the consecutive blasting of groups of borehole charges during the propagation of a seismic blast wave outside the mined block in the Quarternary deposits of a coal mine slope has been experimentally established. The effect of “rocking” the massif occurs stepwise, and it is synchronized according to the selected delay intervals at detonation.