Vol 25 Iss. 1

This article provides an analysis of the electrical equipment diagram of the skip hoist as designed by Yuzhshakhtoproekt (see Fig. 3), as applied to the conditions of the Donbass coal mines. The diagram under consideration assumes operation of the hoist from one horizon. During operation of the hoisting machine, the oil lubrication of the main bearings should function properly.

State triangulations developed in the form of continuous networks based on first-class series extend a single coordinate system over the territory of a mining basin and serve as a basis for developing reference mine survey networks. Using the sides of the state triangulation network as initial ones, the mine surveyor must naturally be able to at least approximately estimate their accuracy. This applies mainly to filling networks of the second class, which still have to be used as a basis for developing mine networks and which in some cases can only with difficulty provide the required accuracy. In this case, the mine surveyor is primarily interested in the errors in the lengths of the sides of the base network involved in scaling the mine triangulation. To perform an accuracy analysis, the mine surveyor usually has only the coordinates of the points and a diagram of the base network. This makes it very laborious to use strict formulas of the least squares method for assessing the accuracy and pushes the mine surveyor to use approximate methods for calculating errors, often not tested in practice. In this article, we study the mechanism of accumulation of errors of the sides and, on this basis, provide an analysis and further development of approximate methods for estimating the accuracy of the sides of a continuous filling network. In this case, we limited ourselves to considering only the errors of the network sides that depend on the influence of errors in the measured values ​​involved in the adjustment of the network, and did not touch on the issues of the influence of errors in the initial data.

During summer ventilation of some workings with low temperatures (acquired, for example, during the winter cooling period), warm atmospheric air, getting into the working, enters into heat exchange with its walls and, cooling, becomes saturated. Therefore, condensed moisture falls on the walls of the working. Its fallout begins from the place where the air flow temperature becomes equal to the saturation temperature. From the same place of the working, where the flow temperature reaches 0°, icing of moisture occurs, which complicates the operation of the working. It is necessary to calculate: 1) icing and condensation thresholds, 2) the thickness of the icing layer, the distribution of temperature along the working as a function of time, air flow velocity, transverse dimensions of the working, temperature and humidity of the atmospheric air.

The efficiency of mechanical installations is assessed by various indicators. A very important one is the efficiency (efficiency), which characterizes the perfection of mechanisms. The practical significance of this indicator is great. The efficiency gives a certain direction to mechanical engineering and establishes optimal operating modes for the operation of machines. It makes it possible to judge the advantage of a combination of mechanisms and significantly simplifies calculation and design work. For example, based on the efficiency values, in many cases friction bearings were replaced by rolling bearings, steam and heat engines by electric motors, the operation of fans is accepted in accordance with the highest values ​​of its efficiency, etc. In the general theory of machines, the mechanical efficiency is determined by the ratio of the absolute values ​​of the work of useful resistances to the work of all driving forces calculated for the period of steady-state motion. Thus, finding the efficiency is connected, firstly, with the clarification of what to call the work of the forces of useful resistance, and, secondly, with the consideration of the work produced only during movement at a constant speed.

The present work is the result of creative collaboration of the Department of Mining Electrical Engineering of the Leningrad Mining Institute with one of the coal trusts. Electric motors of two submersible motor-pumps were tested. The design data of both motor-pumps are absolutely identical. Only their electrical parts differ slightly: the stator of the electric motor of one of them (motor-pump No. 7) has slightly larger slot dimensions than the stator of the electric motor of the other motor-pump (motor-pump No. 9). Therefore, 16 wires are laid in each slot of the stator of the electric motor of motor-pump No. 7, and 11 wires are laid in the electric motor of motor-pump No. 9. The main data of the submersible motor-pumps with a star connection of the stator winding of the electric motor are as follows: electric motor power on the shaft Pn = 9.2 kW; voltage Un = 380 V; revolutions n = 2900 rpm. Three-phase asynchronous short-circuited electric motor (Fig. 1); pump capacity Qn = 30 m³/hour; pump head Na = 50 m. The total height of the motor-pump is 1400 mm, the height of the electric motor is 930 mm, the diameter of the unit is 183 mm. The electrical and mechanical parts of the submersible motor-pumps are manufactured by the assembly and mechanical workshops of the trust. Submersible motor-pumps of the proposed design, used for pumping water from wells, compare favorably with those currently existing in the following features.

The described displacements belong to a special type of fault tectonics, which occurs in cover structures and develops in them as a result of movements of the underlying rigid base. Therefore, displacements of this type are of interest as a characteristic example of tectonics manifestation in the coal-bearing strata of the Lower Tertiary age. A general idea of ​​the nature of the manifestation of displacements is given by the schematic map of displacements and outcrops of coal seams (Fig. 1) and the geological section (Fig. 2). The coal-bearing strata of the Lower Tertiary age (Fig. 2) unconformably lies on the eroded surface of Mesozoic rocks. It is composed mainly of sandy clayey rocks. The underlying Mesozoic rocks in the area of ​​contact with coal-bearing deposits are represented by destroyed conglomerate and quartz-feldspar sandstones.

To increase the accuracy of the heights obtained from a stereo pair, it is natural, first of all, to strive to ensure that one meter of height corresponds to the largest possible increment of the longitudinal parallax at a given scale of the photograph. Or, in other words, one should strive to increase the ratio of the increment (Δр)_i longitudinal parallax by 1 m to the segment (m)i, in the photograph corresponding to 1 m of horizontal extension on the ground. Let us designate this ratio as m. Thus, the value of the indicated ratio acquires a significant role in characterizing the accuracy of height determinations.

The problem considered in this paper arose in the study of the radiation properties of smoke and fog. In the first approximation, these are sols consisting of absolutely black particles. The transparency of the layer can be characterized by the value of the average area in the flow cross-section perpendicular to the line of sight, not covered by sol particles. This point of view belongs to K. S. Shifrin. The need arises to solve the following question: what is the average value of the free area of ​​a limited piece of a plane when n "elementary" regions are located on it, closed and congruent (such an assumption means that a monodisperse sol is considered).

In this paper, we give a solution to a general problem in geometric probability theory, which is the subject of a number of issues in modern technology (aviation agricultural technology, visibility in turbid environments, etc.). Let us consider a set A of points A₀, A..., An, randomly distributed in a circle K of radius R. We assume that the occurrence of each individual point of this set in parts of the circle K equal in area is equally probable (the law of equal probability). Let, further, the number of points in the set A be related to the value of the radius R such that the limit of the ratio exists and is finite. In other words, the average concentration of points in the circle K, with n and R increasing without limit, tends to a finite limiting concentration. We will study the random variable r, which is the smallest of the distances of an arbitrary point A₀ of set A, with its random position in the circle K, to the other points of set A. The random variable under consideration will obviously be equal to the radius of a circle with its center at point A₀, which does not contain other points of set A and has at least one point of this set on its boundary.

In our work "Distribution of stresses in rotating prismatic rods" the problem of determining the stresses in a rod rotating about an axis lying in the plane of the cross-section is solved. This question is reduced to solving two independent problems: the first of them does not depend on the shape of the cross-section contour and can be solved once; the second is reduced to considering a plane strain state. The general solution of the equations of elasticity theory was obtained after long and painstaking calculations by the method of E. Almanzi. We will show that this solution can be easily obtained using the general integral of the equations of elasticity theory in the Papkovich-Grodsky form.

The question of the rationality and necessity of developing thick steeply dipping coal seams prone to spontaneous combustion with backfilling of the mined-out space with waste rock should now be considered finally resolved. In this regard, the choice of the method for performing backfilling operations is of great importance. The correct choice of the method for performing backfilling operations will ensure the production of a stable backfill mass, which will increase the safety of the work and allow coal to be mined without leaving pillars and the associated coal losses. The choice of the method for performing backfilling operations is determined by two main factors: a) the development systems used and b) the nature and properties of the backfilling materials that can be obtained in each individual case. It is clear that when choosing, it is necessary to consider the specifics of each type of backfilling operations.

In the existing calculation methods of mine electric locomotive haulage for determining the elements of motion - traction force, speed and time of movement, energy consumption - an average or equivalent slope of the haulage tracks is usually adopted. An equivalent slope is a constant slope that is equivalent to the actual profile in terms of the operation of traction motors. For newly designed coal and ore mines, a slope of equal resistance or close to it is often adopted in calculations of mine electric locomotive traction, ensuring normal drainage of water from the workings. A slope of equal resistance is understood to be a constant slope at which the traction force of the electric locomotive when moving with a load downhill and the traction force when moving with an empty train uphill will be the same. The calculations imply that the operation of electric locomotives at a steady speed of movement occurs without acceleration, with a traction force and, accordingly, with a current value corresponding to the uniform movement of the train on the adopted constant slope.