Optimization of the ventilation scheme for increasing production capacity of underground mines

Currently, many underground mines are revising their design solutions to increase their production capacity. This tendency is explained by the decreasing ore grades, as well as by the extensive introduction of mechanization in underground mining operations that has improved the output of mobile equipment by increasing the box capacity and engine power. Dieselpowered mobile vehicles are the most common in underground mining practice. The advantages of such engines are obvious as they generate more power than other types of engines. However, the high air demand for mine ventilation limits their application. This is associated with the need to increase the cross-sections of permanent mine workings in order to comply with the standard air flow rate with account of the increased ventilation capacity along with an increase in the inventory of mobile equipment in order to ensure the specified output of the mine. The specific features of mining operations are defined by the stage-wise character of commissioning various blocks of the deposit. Managing of production and development works provides an opportunity to ventilate the mine sections due to their consecutive commissioning, locally, with an isolated stream of air by means of mine workings that do not have the intersection of air streams. This provides a reduction of critical path of air travel up to 30% and reduction of the general mine ventilating pressure drop by at least 20% at constant air flow rate. The results of the work can be used in designing the ventilation system of underground mines both under construction and in operation.

Theoretical basis for the formation of damaging factors during the coal aerosol explosion

Purpose. Assessing the process of damaging factors formation during the coal aerosol explosion in mine workings on the basis of theoretical research of the explosion of coal dust deposits in order to substantiate promising methods of protecting miners from their impact. Methods. An integrated approach is used, which includes a critical analysis of literature data on the occurrence and development of coal aerosol explosions in mine workings; theoretical research into the state of the gaseous medium at the characteristic points of the development diagram of the coal dust deposits explosion as a result of mining operations based on the laws of classical physics and chemistry. Findings. The main aspects of the explosion mechanism of dust in a powdery state, accumulated on the surfaces along the mine working perimeter, and the formation of such negative factors as the effect of gaseous medium accelerated movement, have been revealed; high temperature formed during coal and methane detonative combustion; increased gas pressure. The revealed aspects of the dust explosion mechanism make it possible to determine the main directions for protection of miners caught in the explosion. The diagram of the development of settled coal dust explosion along the mine working with normal ventilation conditions, taking into account the influence of seismic waves, has been improved. Originality. Analytical dependences, reflecting the value of gas energy at characteristic points of the diagram, have been determined, and the dynamics of the formation of negative factors caused by the explosion have been revealed. Practical implications. Possible ways of protecting miners from the impact of negative factors caused by the coal aerosol explosion and reducing the severe consequences of such accidents are proposed.

Experimental research on the haulage drifts stability in steeply dipping seams

Purpose. Substantiation of the conditions for haulage drifts stability using different protection methods in steeply dipping seams based on a set of experimental studies. Methods. To achieve the purpose set, mine instrumental observations have been performed to study the rock pressure manifestations in zonal advance workings adjacent to the stope face on the haulage horizon. The conditions for their maintenance, within the mining site, are assessed by the side rocks convergence value on the drift contour and the change in the cross-sectional area, taking into account the deformation properties of the protective structures. Findings. It is recorded that in the zone of the stope works influence, in the most difficult conditions, haulage drifts are maintained, when coal pillars or clumps of prop stays are used for their protection. It has been determined that a decrease in the section of such mine workings up to 50% is the result of the protective structures destruction. When protecting the hau-lage drifts with the rolling-on chocks, a decrease in the mine working section up to 30% occurs in the process of the protective structures compression. It has been revealed that deformation of coal pillars or clumps of prop stays up to 10-20% leads to a loss of their stability, and an increase to 60% leads to a complete loss of their load-bearing capacity, intensification of rock displacements on the mine working contour and deterioration of its stability. It has been determined that in the process of deformation of the rolling-on chocks from sleepers by 20-60%, they are compressed without loss of load-bearing capacity, which ensures a smooth deflection of the overhanging stratum and restriction of rock displacements on the haulage drift contour. Originality. To study the deformation characteristics of protective structures above the drift, the function of the increment is used of side rock displacements on the haulage drift contour along the mining site length dependent on the relative deformations of protective structures, which makes it possible to assess the real dynamics of the process. Practical implications. When mining steep coal seams, using the specificity of geomechanical processes, which are manifested in an anisotropic coal-rock mass during unloading, satisfactory mine workings stability can be ensured by changing the deformation properties of protective structures above the drift.

SPECIFICS OF DIAGNOSTICS OF TECHNICAL CONDITION OF TRANSPORT AND TECHNOLOGICAL SYSTEM “MINING GAS PIPELINE – MINE WORKING”

The purpose of the paper is to analyze a deformation mechanism of the mine degassing pipelines to forecast their spatial changes in terms of intensification of underground mining of coal-gas seams. Methodology. The paper deals with expert assessment of the available approaches to diagnostics of technical condition of mine degassing pipelines, which are constructed within the in-seam underground mine workings with the floor rocks prone to heaving. The results of scheduled surveying measurements of technical condition of in-seam development workings have helped identify the potentially hazardous zones of rock mass deformation and indices of changes in spatial location of section degassing pipelines mounted in those mine workings. To determine the operating modes of a degassing pipeline under such operating conditions, a computer model of interaction of the elements of transport-technological system “mine gas pipeline – mine working” has been developed Findings. Diagnostics of technical conditions of the mine gas transmission lines and examination of their dismantled components have helped understand that deflections, mainly resulting in water accumulation zones, intensive corrosion of internal pipe walls, and mechanical depositions of coal and rock dust take place right within the flange connection areas. Formation of such zones is argued by health of the degassing pipeline as well as mine air inflow. Availability of internal corrosion, water accumulations, and mine air inflow decreases substantially capacity of the underground gas transmission line inclusive of qualitative characteristics of the captured methane-air mixture and efficiency of MDS on the whole. Originality. New approaches to diagnostics of technical condition of mine degassing gas pipeline in difficult mining and geological conditions of development of gas-bearing coal seams are substantiated and it is offered to consider indicators of their functioning as interacting in space and time transport-technological system "mine gas pipeline - mining". Practical implications. The operational parameters of mine degassing systems notes that the equipment performance with the least underpressure losses created by vacuum pipes requires that the degassing pipeline should have minimum hydraulic resistance of the gas transmission network. Pipeline aeration from the mine workings and water accumulations should be prevented by means of qualitative hermetic sealing of its flange connections as well as the pipeline straightness with the corresponding pitches. Consequently, the basic requirements for operating mine degassing pipelines involve their design profile, tightness of flange connections of pipes as well as operative control of the facility health.

DETERMINING THE PATTERNS OF STABILITY OF MINE WORKINGS FOR CALCULATION ROOF BOLTING PARAMETERS

Purpose. The published studies are aimed at determining the mechanism of deformation of the rocks of the contour around the workings in terms of the parameters of the emerging fracturing and their dependence on the indicators of the strength of the rocks and the depth of occurrence in the massif. The tasks of the study include the installation of fracture indicators, the determination of the parameters of the development of the deformation process around the working, including the effect of longwall mining and taking into account the possibility of reuse of the workings. Methodology. To solve the set tasks, the method of field observations was used together with the use of regression dependencies to determine the dependences of the parameters on the influencing factors. In addition, the method of full-scale pull-out tests of anchor support was used, which made it possible to determine the clamping forces of the anchors. Originality. In the course of the research, the dependences of stresses and deformation along the K7 coal seam in the conditions of the mine named after Kuzembaev CD JSC "ArcelorMittal Temirtau" for the massif around the mine with fastening. Rational parameters for the use of roof bolting in preparatory mine workings have been established. This type of fastening provides direct contact between rocks and lining. Analysis of the results of calculating the parameters of the roof bolting showed that to maintain the roof in the development workings, it is necessary to take into account the parameters of the roof bolting. The main parameters include the length of the anchors, the total resistance of the roof bolting and the density of the anchors. Anchor support forms laminated rock beams in the roof rocks, which ensure the stability of the workings. Conclusions and practical significance. The results of studies devoted to the establishment of the influence of mining-geological and mining-technical factors on the formation of zones of inelastic deformation in the host rocks were considered. Significant dependences of the deformation processes of rocks in the massif around the workings were obtained, and the parabolic zone of destruction of rocks was determined. The practical significance of the research consists in determining the actual indicators of the required bearing capacity of the anchorage at two levels in the conditions of the development of the coal seam k7 of the Kuzembaev mine.

Study of possibility of obtaining alternative binders from production wastes for filling man-caused voids

Basic scientific and practical results of the study of possibility of obtaining alternative binders from production wastes to fill man-made voids at underground ore mining are presented. The objective of the study was to determine the technological possibility and economic feasibility of using available low-active substances as substitutes for expensive and scarce cement. It was shown that it is possible to obtain a binder from dolomite wastes, equivalent in properties to cement, which makes it possible to meet the demands of environmentally correct ore mining technologies. It has been established that hardening mixtures based on dolomites and enrichment tailings are only 8-22% inferior in strength to mixtures with standard cement and are suitable without restrictions for the construction of nature protection massifs in mine workings. Recommended activation of wastes increases the strength of the hardening filling mixture by 15-20% in comparison with the basic technology. With additional preparation in activators, a fundamental change in the quality of dolomite products is possible. The use of wastes in the production of a hardening mixture will free up the land occupied by storage facilities and organize the production of competitive products. Alternative binders and inert materials are recommended for use.

Multi-functional coal mine safety system: visualisation of events (mining processes) form the miner's workplace

The paper reviews the use of mobile video monitoring equipment in coal mines. The most common option is the use of stationary video cameras with real-time video streaming to the mine dispatcher's control monitor via cables. Despite all the benefits of the information obtained, this method has certain limitations due to the specific features of the mine atmosphere, i.e. high humidity and dust levels, as well as the impossibility to organize video monitoring over the entire length of the mine workings. Therefore, mobile video monitoring equipment, both portable and vehicle-based, is efficient supplement to the stationary video cameras. The portable devices include smart phones and the battery-powered head lights with an integrated video camera, which have recently become very popular. In both cases, an important consideration, in addition to the actual video capturing, is the issue of transmitting video data to the top level, i.e. to the mine dispatcher's control panel. The following options are possible: connection to the mine wireless network hotspots via radio channel, reading the information in the lamp rooms when leaving the mine and real-time broadcasting from the mine to the top level. The assumption is made that in order to implement the fastest (and the most efficient) way that works without delays between capturing and transmitting of video data to the daylight surface, such as the latter of the options above, a communications infrastructure based on wireless and cable networks needs to be deployed in the mine workings. The required infrastructure is present in a number of systems designed to locate miners inside the mine workings as part of a multifunctional security system, which enables continuous radio communication of individual devices with infrastructure nodes and, therefore, real-time video data transmission.

DYNAMICS OF GAS EMISSION FROM EXPOSED SURFACE OF GAS-BEARING COAL SEAMS HAVING MEDIUM THICKNESS

The goal of the research was to clarify the regularities of the dynamics of gas release from the surface of the outcrop of the developed coal seam. The main research methods were theoretical methods of mathematical physics and non-equilibrium thermodynamics. Gas-bearing coal seams are usually mined underground. When driving development workings, outcropping surfaces of gas-bearing coal seams appear and gases in the seams under excessive pressure are released into the atmosphere of the mine workings. Gas-bearing coal seams are usually mined underground. When driving preparatory workings, surfaces of outcropping of gas-bearing coal seams arise and gases that are in the seams under excessive pressure are released into the atmosphere of the mine workings. The most important gas-dynamic characteristic of this process is the rate of gas release, which represents the volume of gases released from a unit area of exposure of a coal seam per unit of time. A generalized law of resistance for gas filtration in a rock mass is recommended, and a fairly rigorous thermodynamic substantiation is given. It is shown that the densities of gas mass flows in accordance with the postulate of their linear relationship with the driving forces are determined by the Onsager relation. The results obtained and their discussion is presented. Mathematical models are proposed for engineering calculations of the dynamics of methane release from the outcropping surface of medium-thick coal seams. The error of the adopted approximations does not exceed 3%. The intensity of methane release is directly related to the planogram of work in the working face. Analysis of this dependence indicates that during the extraction cycle, methane release increases due to an increase in the area of the gas-release surface. The main conclusions are as follows: mathematical modeling of the processes of gas movement in a porous sorbing medium using approximate mathematical models representing linearized equations of mathematical physics; the regularities of the dynamics of the rate of gas release from the surface of the outcrop of a gas-bearing coal seam is the theoretical basis for the mathematical description of the process of gas release; the use of a linearized hyperbolic filtration equation most accurately describes the processes of methane release from the outcropping surface of mined coal seams.