Recently, there has been a marked increase in the use of large-volume workings, both in the development of deposits and in the construction of underground chambers for various purposes, transport tunnels, etc.For normal operating conditions, definite parameters of the atmosphere must be maintained; this is associated with the supply of considerable volumes of fresh air and hence with increase in the energy consumption.It is of great practical value to know the velocity field and turbulent viscosity over the volume of the underground chamber, since these factors determine the conditions for the creation of normalized parameters of the mine atmosphere.In most cases, the ventilation of chamber-like workings is calculated analogously to the approach in [i, 2], which permits the analysis of the scattering and entrainment of harmful impurities by ventilation jets, without taking account of inhomogeneities in the velocity field and the turbulent diffusion coefficients.The aim of the present work, a continuation of [3, 4], is to create methods of mathematical modeling of the turbulent ventilation of slot-like chambers and large-volume workings.Existing methods of calculating mine-working ventilation are based on the mean velocity of mine-air motion. At the same time, almost all investigations of mine ventilation in large chambers [2, 3, 5, 6] conclude that the velocity field there is complex, because of the presence of recirculation zones and breakaway flows.It is evident that detailed calculation of the velocity field is required to solve the impurity-transport equations.The fastest and simplest way to find the velocityfield in a chamber-like working of arbitrary form is to construct a mathematical model of the turbulent motion of an incompressible atmosphere [3, 5]. In the simplest two-dimensional case, following [3], the nonsteady NavierStokes and continuity equations, averaged over the time and one coordinate (the chamber height, in the present case) according to the Reynolds rule, can be written in the form 8UOV aU + U.~ + V. a-F =-----a--~where U and V are the components of the mean velocity along the coordinate axes x and y; ~ij is the Reynolds stress; P is the mean pressure; p is the density of the mine atmosphere (assumed constant): t is the time.The expression for the Reynolds stress introduced by Boussinesq for a flow of general form includes the turbulent viscosity, ~t, specification of which permits closure of the system in Eq. (i). A great variety of methods of such closure is known.Four models are realized for the problem of the ventilation of chamber-like workings. A: Simplest ModelConstant turbulent viscosity is assumed.Although this hypothesis is invalid at the axis of the jet flows, it can be used in the recirculation zones and the near-wall flow for approximate calculation of some simple turbulent flows.S. M. Kirov Mining Institute, Academy of Sciences of the USSR, Kazan' Branch, Apatity.

In order to solve practical problems in mine aerology concerned with room-type workings of large horizontal area, we have to study the laws of distribution of so-called "free" jets in a confiued space. One of the principal parameters of the jet is the angle of divergence ~ due to turbulent diffusion and entrainment of the surrounding liquid. Since no general analytical solutiou has been found for ~, it is usually determined experimentally. The most detailed results of determination of the angles of divergence of a jet are given by Linzer [1], who processed experimental data due to Abbot and Klein [2], Krall and Sparrow [3], and others.In Fig. 1 we see a situation which, on the one hand, is analogous to the initial conditions, and, on the other, is different in structural elements from those described in a study [1][2][3] of the flow around a doubly symmetrical bench with sharp edges.

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A large proportion of nonferrous and rare metal deposits are of a small or medium thickness. These deposits are normally worked by open pit mining. The working spaces are chambers of different configurations filled continuously or periodically with toxic production materials. The types of chambers investigated in this study are slotlike workings with width and length greater by two orders of magnitude than their height; both by geometric parameters and by ventilation conditions, these workings differ significantly from the situations described in the literature and investigated by various authors [1][2][3][4].Our studies have shown that the process of equalization of concentration of gas products in chamberlike workings is protracted in time, i.e., the concentration leveling occurs both over the cross section and along the working length. The geometric parameters of a chamber change as the mineral is extracted, leading to altered aerodynamic conditions of advancing space and ratios of dilution and outflow of gas products, as well as altered concentration leveling times.When the working is advanced along the strike of the ore body (from the center to the flanks of a block), the ventilation of slotlike or flat chambers at the initial stage of the working of a block is conducted by a combined Jet, i.e., a free jet operates in the part of the chamber adjacent to the air supply opening while in the further portion (after it is opened up to the chamber boundaries), there develops a limited turbulent flow. As the working approaches the block boundaries, the ventilation of the chamber occurs by the action of vertically limited free Jets [5]. The process of ventilation of a flat chamber should therefore be considered in the dynamics of the progress of mining operation, i.e., with a gradual increase of the width of the chamber Bk.Without going into the aerodynamics of the stope spaces that had been analyzed earlier [5, 6], we will consider the diffusional distribution of impurities in turbulent flows.Figures la-c present the general results of all processes occurring in a chamber along the x and y axes as oscillograms of the impurity concentration variations in time. These results are aggregated for a large number of experiments (more than 20 for each situation). The process was recorded using a mirror-galvanometer oscillograph at the output from the hydraulic model (Fig. 2), using electrode sensors. The resultant variation curves of c f(T) are characterized by a certain effective turbulent dlffusivity.When activating the hydraulic model, the impurity, simulated by 1% NaCI solution, was instantly injected through a perforated pipe with openings of u -1 mm, oriented in the vertical plane, i.e., the injection process obeyed in time a 6-function (Fig. 3, curve I). Analysis of one of the unit oscillograms (Fig. 3, curve 2) showed that the original jet pulse brings out of the chamber (through the input channel) a portion of the impurity in a concentrated form, partly diluted through distension of the gas Jet (turbulent deformat...

Studies by Soviet mining undertakings have shown that equipment with diesel-engine drives is being increasingly used, but the consequences of the change have not yet been fully evaluated from the technicoeconomic aspect.Pollution of the working atmosphere with harmful gaseous emissions causes a significant deterioration in the working conditions for the miners. An improvement in the working conditions when diesel-driven machines are used is therefore a matter of urgent priority.Mathematical simulation of the combustion of fuels and the treatment of the gaseous emissions has been used widely in an effort to find effective protective measures against the harmful components of diesel exhaust gases.The basic approaches to the development and use of a mathematical model for this purpose are given in [1][2][3][4].The principle of local equilibrium, which truly reflects the physical characteristics of combustion processes, was used by [1][2][3] to develop a mathematical model.The model solved, with high accuracy, many problems related to the selection of fuel mixtures for the minimum gaseous emission.But the question of the qualitative and quantitative conversion of the exhaust gases by reaction with liquid neutralizing agents, under the conditions determined by the model, remains unresolved.Changes in the nonequilibrium composition of a system with time, can be established from the rates of chemical reaction by physicochemical kinetic methods. With a knowledge of the kinetics, type and order of the reaction, and the quantitative values of the velocity constants, it is possible to obtain a general picture of the behavior of a physicochemical system over a period of time. However, the absence of reliable empirical quantitative data frequently restricts the use of kinetic methods in many applications.Momeover, the solution of physicochemical problems by thermodynamic equilibrium methods alone frequently fails to give the desired results.In such cases, apart from the equilibrium conditions, it is necessary to consider those processes which obey the kinetic laws and also the constraints of the physicochemical equilibrium model, with all the advantages and merits incorporated in the kinetic component.A new method of solving similar problems by substitution has been proposed, based on splitting a complex system into mutually overlapping subsystems: thermodynamic and kinetic. The thermodynamic subsystems relate to the phases and their dependent components, which obey the thermodynamic equilibrium criteria.The kinetic subsystems relate to the phases and their components (dependent or independent) which vary in accordance with kinetic laws. The chemical characteristics of the process impose limitations on the equilibrium of the subsystems of the complex system at each particular moment in time.These additional limitations, together with the overall limitations based on the mass balance, can modify the equilibrium solution based on the minimum isobaric--isothermal potential of the complex system. The simulation may be made in two...