The results of the analysis of statistical data on accidents at Russian mines caused by explosions in the workings space have shown that explosions of methane-dust-air mixtures at underground coal mines are the most severe accidents in terms of consequences. A detailed analysis of literature sources showed that in the total number of explosions prevails total share of hybrid mixtures, i.e. with the simultaneous participation of gas (methane) and coal dust, as well as explosions with the possible or partial involvement of coal dust. The main causes contributing to the occurrence and development of dust-air mixture explosions, including irregular monitoring of by mine engineers and technicians of the schedule of dust explosion protective measures; unreliable assessment of the dust situation, etc., are given. The main problem in this case was the difficulty of determining the location and volume of dust deposition zones in not extinguished and difficult to access for instrumental control workings. Determination of the class-shape of coal dust particles is a necessary condition for constructing a model of the dust situation reflecting the aerosol distribution in the workings space. The morphological composition of coal mine dust fractions with dispersion less than 0.1 has been studied. Particle studies conducted using an LEICA DM 4000 optical microscope and IMAGE SCOPE M software made it possible to establish the different class-shapes of dust particles found in operating mines. It was found that the coal dust particles presented in the samples correspond to the parallelepiped shape to the greatest extent. The mathematical model based on the specialized ANSYS FLUENT complex, in which this class-form is incorporated, is used for predicting the distribution of explosive and combustible coal dust in the workings space. The use of the obtained model in production conditions will allow to determine the possible places of dust deposition and to develop measures to prevent the transition of coal dust from the aerogel state to the aerosol state and thereby prevent the formation of an explosive dust-air mixture.
The methods of evaluation of the aerological conditions to be performed for the purpose of normalization of mining conditions are provided in the present review; the location of possible accumulations of explosive gases during the drift of the development workings are taken into account. To increase the safety of the development working regarding the gas factor, a complex evaluation of a working was developed with respect to the dynamics of methane emission and air coursing along the working which is strongly affected by the character of the leakages from the ventilation ducting. Thereby, there occurs a necessity of the enhancement of a methodical approach of calculation of ventilation of a working which consists in taking into consideration a total aerodynamic resistance of the booster fan including the local resistances of the zones of the working. An integer simulation of the gas-air flows realized on the basis of a software package FLowVision allows to evaluate a change in the methane concentration in the zones of local accumulations.
The article describes the methods for gas balance definition of working area with face zone isolation from mined-out space, that have allowed to change the air distribution in face zone and to determine the part of evolved gas from bed and marked bed.
The article describes the necessary conditions for similarity parameters choosing for aero-gas-dynamic modeling with main roof collapse and it has been made analysis of them.
The article describes the formulas for calculation of air flow characteristics, that originates from the main roof collapse and also it has been made analysis of variates, that form their parts.
Problems of environmental protection are especially topical for areas of metallurgical industry location. Almost all steps of metal production are attended by powder and gas formation, that are injected with technological and ventilation emission. Minimal negative effects in eco- systems are expected in the case of use technology with the highest level of closed-circuit system, which inject pollution agents to the number that is responded for ecosystem capacity.
A method for calculating the required amount of air for gas ventilation of the internal combustion engine of railway tunnels has been developed. This method takes into account such provisions as the direction of air movement to the direction of train movement, train speed and the number of trains simultaneously in the tunnel. Cases such as a train standing motionless with the engine running, train movement towards and against the direction of airflow, and cases of multiple trains in the tunnel are analyzed. For all variants, calculation equations of the required air quantity and recommended train speed that can ensure the concentration of pollutants in the tunnel below the MAC (maximum permissible concentration) are proposed.
The main factors determining the peculiarities of accident-free operation of railway tunnels under windless climate conditions are considered. It is shown that ice formation caused by a combination of two unfavorable phenomena: relatively low air temperature in the tunnel and high watering of the tunnel is especially dangerous. The paper presents the results of the experimental studies indicating that the gas composition of the tunnel air is determined not only by the harmful gaseous impurities emitted by the carriers but also by methane, carbon dioxide, hydrogen sulfide and radon coming from the surrounding rocks and water. The mechanism of radon impact on tunnel personnel has been studied and a large-scale description of its possible impact on air quality in the tunnel has been given. Many regions of the Russian Federation, including those where the longest railway tunnels of Russia are located: Baikalskiy and Severo-Muiskiy, can be classified as radon hazardous. Creation of rational ventilation conditions influencing not only the radiation situation but also the thermodynamic characteristics of the air should be considered as a fundamental means of achieving the required air quality in the tunnels. In order to increase the stability of ventilation conditions the possibility of using different regulating devices has been studied. The maximum influence on the air flow is exerted by the installation of a ventilation door, which allows to change the air inflow by 70% of the initial indicator. The principles of creation of the favorable temperature conditions in the railway tunnels, which is one of the effective means of ice formation prevention, have been implemented and tested on site.
Производственными исследованиями по специально разработанной методике установлено, что при столбовой системе разработки калийных пластов Старобинского месторождения имеет место выделение горючих газов в действующие горные выработки. Основным компонентом этих газов является метан, в незначительных количествах выделяются тяжелые углеводороды. В обычных условиях абсолютное газовыделеяие на выемочных участках незначительное. В общем газовом балансе участков основную часть (до 98 %) составляет газовыделение из выработанного пространства.
Поддержание подготовительных выработок в хорошем состоянии является одним из условий, определяющих нормальное развитие очистных работ ...
Устойчивость горных выработок в большой степени зависит от формы их поперечного сечения и соответствующего очертания крепи. Однако это общеизвестное положение часто не учитывается, в результате чего несущая способность крепи используется не полностью ...
Четырехшарнирная крепь представляет собой статически определимую геометрически изменяемую систему с одной степенью свободы. В наземных конструкциях геометрически изменяемые системы почти не применяются ввиду их неустойчивости. Поэтому конкретной методики их расчета строительная механика не дает ...
