V. P. Efimov

Interaction of geomechanical and physicochemical processes in Kuzbass coal

The paper presents laboratory and in situ research data on interaction of geomechanical and physicochemical processes in Kuzbass coal of various ranks, considering temperature effect. Under analysis is the relation of stress-strain state, temperature and infrared radiation of coal. The authors study the role of temperature and microstructure of coal in energy and mass exchange processes (variation of mass, volatile yield, specific surface, internal energy of methane adsorption capacity decrease and moisture content). Interrelation of outburst hazard and fire hazard in coal is discussed from the viewpoint of uniform stagewise thermomechanics and thermochemistry of coal behavior in the course of coal formation and extraction. The article introduces a generalized factor for quantitative description of petrographic properties of coal. Using this factor, the authors classify and describe petrographic groups of Kuzbass coal.

Gradient Approach to Determination of Tensile Strength of Rocks

Using Brazilian method, the strength tests of rocks and model media are carried out on the cylindrical samples with hole. On the basis of gradient approach, a procedure is developed for calculating the tensile strength.

Determination of tensile strength by the measured rock bending strength

The paper discusses the data of four-point bending strength for various rock types. Different nonlocal strength criteria are applied to the tensile strength assessments based on measuring the bending strength. The tensile strength calculated using a bar bending model under plastic deformation turns out to be the closest in value to the experimental strength.

Effect of loading rate on fracture toughness within the kinetic concept of thermal fluctuation mechanism of rock failure

Based on the strength and crack resistance tests of dolerite and gabbro–diorite samples subjected to bending as a function of loading rate, it is shown that the kinetic constants of strength in Zhurkov model have the same values in the localized and non-localized failure modes. The tests on destruction of an organic glass sample with an edge crack yield the similar results.

3D modeling of fracture growth in solid under the penetration of rigid wedge

The authors have undertaken experimental and theoretical modeling of fracture growth under the penetration of rigid wedge in brittle rock. The test specimens were made of organic glass to facilitate measurement of size and shape of a fracture. The wedge loading was executed quasi-statically on a testing machine and dynamically by a drop wedge. The scheme developed in the framework of the theory of elasticity for the theoretical description of the fracture growth process accounts for the finite size of the wedge cutting point and the influence of free surface. The theoretical and experimental shapes of fractures are compared.

Tensile strength of rocks by test data on disc-shaped specimens with a hole drilled through the disc center

The author reports test data on disc-shaped specimens of rocks and model media with a hole drilled through the center of the specimens loaded along the diameter. The test data processing uses non-local fracture criteria. The calculated destructive forces are compared with the measured destructive loads. Based on the tests of specimens with the central through holes, the tensile strength algorithm is presented.

Modeling the striking head-impact tool-rock mass interaction

The authors have designed a stand with a pendulum drop hammer to model the hammer head-impact tool-rock mass interaction. The rock mass is simulated by an adjustable gas-liquid dampener, metal plate and marble block. The comparison analysis includes measured impact pulses in the striking head and impact tool, and the influence of the striking head velocity recovery factors on interaction of the striking head and impact tool with the dampener and rock block.

Express Method for Estimation of Tensile Strength and Crack Resistance of Brittle Media

The procedure is proposed for estimating the crack resistance and tensile strength of rocks by the results of experiments on disk samples with holes. The gradient approach to the strength problem is employed in processing the experimental data.