According to "Safety rules at coal mines" [1] and "Recommendations for the choice of efficient modes of mines ventilation during accidents" [2] at the mines of Ukraine during the preparation of emergency response plans should be assessed on a firm downward ventilation of mine workings under exogenous fires. Such an assessment is conducted twice during a year within preparing a new plan for an emergency.

Assessment of the ventilation stability during fires in inclined workings

According to [2,3] during determining of the mine ventilation stability are calculated values of the fire thermal depression and simulation of its effect to mine ventilation network.

Depending to the specific conditions thermal depression can be determined by metering or calculation methods. The first method gives the most reliable results.

Consider a metering method for determining of the thermal depression. Inclined or vertical working, in which the fire occurred, can be ventilated by descending or ascending air currents. If the thermal effect of depression is opposite to that of depression, which creates by the main ventilation fan, then increase the energy losses on the movement of air, which increases the pressure differential between the ends of the emergency working. In the case where the thermal depression acts in the same direction as the depression of main fans, energy consumption for air movement are reduced, so the difference in pressure between the ends of working is also reduced. Determining of the thermal depression that occurs within fires in the slope with a downward movement of air is necessary to make the following measurements:

Difference in pressure between the ends of the emergency working (determined by micromanometer or devices such as barometric type; for laying of rubber tubing used parallel workings);

Airflows consumption in the emergency working, which are measured above for the fire.

The value of the thermal depression is calculated as follows:

h_т=h_а.з + h_а.р

Research of mine workings ventilation stability in the mine "Trudovskaya" during fires in the normal and reverse modes of ventilation

In this master's work will be performed research of air flows stability during fires in inclined workings of top-down and bottom-up ventilation. Researches of stability will be conducted by using the program complex «IRS Вентиляция шахт-ЭПЛА».

The first phase of work involves creating a computer model of the mine ventilation network and its testing [5,6]. The second phase will focus on the modeling of fires in inclined workings and analysis of simulation results. During the third phase will be developed measures that help to improve ventilation stability. Researches include searching of installation sites for air regulators to enhance ventilation flows stability, determination of the aerodynamic resistance and checking the effectiveness of the proposed activities on a computer model.

A feature of this work will be simulation of fires in inclined workings included to the zone of general mining reverse ventilation. In Ukrainian mines determination of ventilation flows stability in the reverse mode ventilation is not provided. However, analysis of the possible consequences allows to suggest that during a fire in the working with downflow and the subsequent reversal of resistance may prevent ventilation stability. In these cases, appears an additional threat to the life of miners and rescuers.

Modeling of reverse mode ventilation will be conducted by a special technique developed at the Department of «Occupational safety and aerology» DonNTU [4,7].

Developed method

In the program complex «IRS Вентиляция шахт - ЕПЛА" action of maximum thermal depression is envisaged, and for modeling of the reverse mode with a maximum air flow costs is enough to put a minus sign (-) in front of the coefficient A (optional depression) in model of each of main ventilation fans. In reality, for the general reverse ventilation it is necessary to include several winches for removing metal doors (lyad), stop acting fan(s) of the main ventilation and switch on backup fan(s). Thus script of reakity (events switches on-movement on a real physical object) is replaced by the concept of simulation (one event - appearance of the minus sign before the number that defines an "optional depression" in a computer program).

Further "deployment" of modeling scenario depends of the effects of modeling. If, in the first variant of modeling air resistance is not conserved, so further researches are meaningless - the result obtained. When air resistance is permanent we simulate next variant of the air distribution. In this case, provide a normalized flow rate (60%) in the reverse mode without changing of the ventilation facilities resistances. It is sufficient to reduce an additional depression in the tree modeling fan in 2.77 times.

When air resistance is permanent we simulate the third variant of the simulation. It provides normalized changes of the aerodynamic resistance of ventilation buildings in ducts of fans in mine workings [1].

Last variant of general mining simulation of reverse mode ventilation performing if during the previous scheduled reversal of ventilation have been identified aerodynamic resistances of all ventilation ducts and mines workings with ventilation facilities. For simulation enough to change (where necessary) aerodynamic resistance of the appropriate branches of the mine ventilation network.

Obligatory condition of simulation is the account of the natural draft in the vertical and inclined mine workings.

In all cases, when modeling of general mining ventilation reverse mode indicates a potential opportunity violation of the ventilation stability during a fire in the slope, it is necessary to provide special measures for the safe rescue of miners and emergency.

Ventilation reverse mode simulation on functioning Ukrainian mines showed that disturbance of the air flow stability (during fires in inclined workings within the zone of reversal) is possible in 40% of cases.

The first time was researched ventilation stability during a fire in inclined workings after general mining reversal of ventilation in conditions of the mine «Trudovskaya». During of special researches performed:
- simulation of general mining reverse ventilation;
- selecting of sites for the ventilation controls installing;
- determination of the aerodynamic resistance of regulators;
- test for effectiveness of the developed activities.

A summary of the Master’s thesis:

In the master's work on a computer model of the mine "Trudovskaya" was assessed air flow stability in the workings with top-down and bottom-up ventilation for normal and reverse modes of ventilation.

In the course of the work was developed a computer model of the mine «Trudovskaya». The model consists of 262 branches and 226 knots. 4679 indicators characterizing geometric dimensions and aerodynamic parameters of workings and the main ventilation fan were introduced to the model database.

Defined zones spread of fire gases in the normal and reverse modes of ventilation.

Defined workings in which occurred air flow overturning and were analyzed conditions under which happened these rollovers.

Conducted researches and was made a choice of sites for ventilation controls installation. Defined the necessary aerodynamic parameters of the ventilation controls.

Audited performance of the developed measures.

Examples of simulation of fires

,

Figure 1. Simulation of a fire in the working with a descending ventilation

Red - emergency working.
Yellow - zone of fire gases spread before air flow rollover.
Blue - zone fire gases spread after air flow rollover.

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Figure 2. Simulation of fire in the working with ascending ventilation

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Animation 1. Simulation of fire in the working with ascending ventilation in case of general mining reversed ventilation

Conclusion :

At the present time in the master's work were researched ventilation stability in workings with downward and upward ventilation during fires and have been developed measures to improve stability. Subsequently it will be simulated general mining reverse ventilation and research stability of ventilation in the emergency ventilation mode.

Literature:

1.Правила безопасности в угольных шахтах. – К.: Держохоронпраці. – 2005. – 398 С.

2.Рекомендації по вибору ефективних режимів провітрювання шахт при аваріях// НДIГРС. — Донецьк. — 1995. — 165 с.

3.Болбат И.Е., Лебедев В.И., Трофимов В.А. Аварийные вентиляционные режимы в угольных шахтах — М.: Недра, 1992 г.,— 204с.

4.Трофимов В.О., Л.В. Незамова. Компьютерне моделювання аварійних вентиляційних режимів. Вісті Донецького гірничого інституту: Всеукраїнський науково-технічний журнал гірничого профілю/ Донецьк: ДонНТУ, 2009. – №2 – С.97-100.

5.Каледіна І.О., Романченко С.Б., Трофимов В.О. Комп'ютерне моделювання шахтних вентиляційних мереж: Методичні вказівки. — М.: Видавництво МГГУ. 2004 72 с.

6.Каледіна І.О., Романченко С.Б., Трофімов В.О., Горбатов В.А. Комп'ютерне моделювання задач протиаварійного захисту шахт: Методичні вказівки. — М.: Видавництво МДГУ. 2004 — Частина 1. — 45 с.

7.Трофимов В.О., Булгаков Ю.Ф., Кавєра О.Л., Харьковий М.В. Аерологія шахтних вентиляційних мереж. — Донецьк, 2009. — 87 с.