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In the modern theory of rock cutting in production conditions, it is customary to distinguish two large classes of achievable cutting modes – relieved and unrelieved. The kinematics of rock-breaking machines in most cases determines the operation of the cutting tool in both modes in one cycle of the cutting tool. The currently available calculation methods have been developed for a stable, usually unrelieved cutting mode. In this article, the task is set to determine the conditions for the transition between cutting modes and the modernization of the calculation method for determining the forces on the cutting tool. The problem is solved by applying methods of algebraic analysis based on the search for the extremum of the force function on the cutter, depending on the ratio of the real cut spacing to the optimal spacing for the current chip thickness. As a result of solving the problem, an expression is obtained for determining the chip thickness, for which, at the specified parameters, the transition between the relieved and unrelieved cutting modes is provided. The obtained result made it possible to improve the method of calculating the forces on the cutting tool in the areas of the cutter movement with relieved cutting.

The authors justify a computation model of a machine percussion system simulated by elastic cylindrical rods subjected to maximal axial load at minimal strain. Rock mass is assumed as a perfectly solid block. The piston and tool are described by the values of length, cross-section area, density and Young’s modulus. The model determines the force applied by the tool on the rock as function of time. It is assumed that transverse displacements and velocities of the rods are negligeable as compared with the axial displacements and velocities, while the rods are free from the action of the external forces different from the restraining forces. The variational equation expresses the principle of possible displacements. The variations are independent of time. The initial and boundary conditions are considered. The variational equation is solved using the method of straight lines, with replacement of a time differentiation operator by the finite difference operator. The problem reduces to the successive solving of boundary value problems with variable right-hand sides. The finite difference scheme is the approved implicit scheme of Crank-Nicolson. The boundary value problems are solved using the finite element method at each step of integrating. As a result, the variational equation transforms into a system of linear algebraic equations, and the reduced solution of this system yields the wanted force. The calculations are illustrated by the tool press force-time curve plotted with a step of 0.1 µs for hydropercussion machine G100 by Rammer, Finland. The relative calculation error of the impact duration and maximal force (in absolute magnitude) is not higher than 0.1%.

One of the promising methods for rock cutting technology is the use of high-speed water jets. In order to improve the cutting capacity of water jets without increasing the hydraulic power of equipment, pulsed water jets are basically used to increase the rock cutting efficiency. However, there are no mature recommendations for selection of rational parameters, and the relationship between indicators of rock cutting efficiency and parameters of pulsed water jet is still not established. In this context, we aimed at developing a generalized equation for calculating rock cutting efficiency, in which all the major parameters in consideration of rock cutting process are included. Then, a calibration of the rational parameters of rock cutting by pulsed water jets was conducted. The results are likely helpful for increasing productivity and reducing energy consumption. Keywords: Pulsed water jets, Rock cutting, Water jet technology, Generalized equation, Depth of cut

The features of the selection and calculation of the main elements of the shield machine with the ground-cutting head and the type of its support are considered. The requirements for the bottom-hole chamber and its elements, the system of stabilization of the face of the shield machine and equipment for injection of additives are described. It considers the issues of design of mixing devices and systems for removal of soil.

Considered selection and calculation of cutting head for earth pressure balance tunnel boring machines. The conditions of choice of the working body are defined. The possible types of cutting heads and the features of choosing the type of their supports and drive mechanisms are described. The dependence for the calculation of the torque on the working body is given. The recommendations on the choice of the degree of openness of the cutting head, the type of destructive tool, expansion devices and seals of the bearing units of the drive of the working body depending on the ground conditions of penetration.

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.

One of the main topics in modern mining science is the prediction of the excavation performance. The most used indicators describing excavation efficiency are specific energy and cutting force. At this the last one is of primary concerns of practicing engineers and researchers. Cutting force depends on physical properties of a destructed rock, tool’s geometry and technical parameters of the process such as penetration, spacing, etc. Rock properties are almost always considered as unchangeable parameters of the process. So in order to use rationally limited power resources of a machine mechanical excavator’s manufacturers and miners only optimize tool’s geometry and technical parameters of the process. Most of them are hardly changeable during exploitation. Thus, it is a responsible challenge to estimate optimal values of the parameters that is not still properly executed. The proposed approach is a mathematical, which defines cutting force as a function of a variable. It depends on estimation of such a value of the variable that relates to a specific relation λ between changes of the argument δχ and the function δy. The approach could be used not only on the designing stage of a project but also for in-situ decision-making on the changing of a specified parameter depending on permanently build function of cutting force.