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Purpose. To determine an influence exerted by the cutting mode and by geometry of cutters on the impact loads in various scenarios of cuttersolid inclusion interaction. Methodology. Mathematical simulation, statistical analysis Findings. Fracture of coal seams of a complex structure which contain solid discontinuities (solid inclusions and hard dirt bands) is associated with generation of impact loads on cutters and cutting heads of mining machines which cause a decrease in the productivity of the coal extraction process and premature failure of their components and elements. This impairs efficiency of coal cutting and causes premature failure of different components and parts. It is found that when a cutter cuts an inclusion or touches it, the size of the inclusion has no influence on the value of the peak load. On the contrary, in case of tear-out of an inclusion, the peak cutting force value essentially depends on the size and shape of the inclusion, as well as on the brittleness and plasticity of coal as these properties govern coal-inclusion cohesion. It is found that out of all modes of cutter-solid inclusion interaction, the highest loads arise in the mode of central cutting of inclusions. The mechanisms and behavior of occurrence of loads in short-term cutting of large (unbroken) solid inclusions by a group of cutters are discussed. The maximal loads on groups of cutters on cutting heads can also arise in gradual stalling when the average loading level approaches the tractive effort torque of electric motor when a group of cutters cuts many solid inclusions simultaneously, or in undermining of roof rocks, or in cutting hard dirt bands. Originality. The probabilities of solid inclusion cutting by a cutter are determined for different outputs of a cutting head, and the action times of the maximal peak load in cutting a coal strip 100 m long are assessed. The relations are proposed to calculate the levels and action times of maximal loads on a group of cutters in cutting solid inclusions, as well as the coefficients of variation in the loads and the loading inequality of a cutting head. Practical value. The results obtained by the authors should be taken as a basis in determination of the maximal instantaneous torque in the cutting head transmission to be used later on in calculation of the long-term strength of the transmission components.

The paper describes an experience in the field of slant directional drilling in oil industry, which is currently under pressure. The experience helping to meet drilling projects’ challenges in an effective way has been approved for a several years of work at quite a few projects in different countries. The paper includes some design and technological tricks to overcome standard problems arising during slant directional drilling of oil wells such as entering the ground, maintaining the drilling trajectory, adjusting of an axis misalignment between the rig’s central shaft and the drill line, choosing proper pumps and adjusting pumping pressure, and keeping the drill rods and casings from sliding into the hole from an inclined mast.

Development of technical means of excavation for tunnelling and minerals extraction requires the use of relevant experience and brand-new scientific achievements in the field of rock destruction by mechanical tools. Important problems of the use of rock cutting tools are wearing and tool consumption, which influence technical and economical performance of mining projects. Therefore, the paper provides an overview of existing domestic and abroad methods for determination of abarsivity of rocks, which are testing methods by Baron and Kuznetsov and by CERCHAR. The paper provides with a description of the essence of the method for determining the Russian abrasivity index and CAI, equipment for their implementation, as well as requirements for the styluses and rock samples. It is also given the classification of rock abrasiveness according to both methods. The important conclusion, which can be made based on this study, is that Russian abrasivity index by Baron and Kuznetsov can be correlated with CAI as we have done it in the first approximation.

Screw modules are widely used in technological and transporting machines. Their main disadvantage is low productivity due to the fact that the material moves partly in the direction of the feed and partly rotationally as a result of the torque transmitted by the screw blade to the material. The rotational component of the material movement significantly reduces the performance of the screw. The work considers the possibility of mining machines with screw modules efficiency improving by determining the rational screw shaft configuration, depending on the properties of the feed material and the operating conditions of the module, realized at the designing stage. The aim is achieved by means of a mathematical description of the screw feed process that takes into account processes occurring both on the surfaces of the material contacts with the working bodies of the machine and inside the material mass, including the occurrence of a sliding surface in the material. Furthermore, some part of the material sticks to the screw and moves in concentric circles, with no axial movement in the feed direction, which reduces the performance of the screw. The screw shaft configuration is determined by means of design procedures based on the mathematical description of the screw feeding process, given in the work. The description takes into account the processes occurring in the mass of the feed material. The resulting mathematical model of the screw feeding process allows designing screw shafts with shape identical to the sliding surface in the material, which will increase the performance of the screw module by 20-23%, by reducing the rotational component of the material movement and increasing the translational component in the feed direction.

The article examines the screw modules of technological machines that feed materials under pressure and move loads in the vertical direction to various working bodies. The main disadvantage of these screw modules is low productivity due to the spiral movement of the material, with a significant deviation from the longitudinal axis of the screw module. The paper considers the possibility of increasing the operational performance of screw modules of technological machines by reducing the rotational component of the material movement. This goal is achieved by installing ribs on the inner surface of the module. The angle of ribs installation is determined by the kinematic and geometric parameters of the conveyor auger shaft and the properties of the supplied and moved loads. The results of theoretical studies show that correctly selected geometrical parameters of the ribs can increase the screw module productivity by 18 – 20%.

The article analyzes indexes that characterize properties of coal seams and are used in calculation of loads on cutting tools of mining machines, or in selection of drives. Determination of geological structure complexity of coal seams takes into account hard inclusions and dirt bands in coal, as well as their size and lithology type. The notion of coal cuttability in spalled and unspalled face zones is explained using the coefficient of coal spalling. For strength estimation of complex structure coal seams with dirt bands and hard inclusions, it is proposed to use the index of integral cuttability which is the sum of coal cuttability and generalized index of densities and properties of inhomogeneities in the seam. In geological documentation, strength characteristics of inhomogeneities are described using the ultimate compression strength or Protodyakonov factor of hardness (in Russia). For this reason, the authors propose an empirical expression to recalculate cuttability of inhomogeneities in terms of uniaxial compression strength or hardness factor. The estimation algorithms of brittleness, grindability and breakability of coal seams are presented. The formula of coal abrasiveness is given. Systematization of data on breakability of coal seams has made a framework for classification of coal seams as media disintegrated by cutting tools of mining machines.