Heat and mass exchange in newly driven mine workings

Heat, smoke and other toxic products may spread along the tunnel, in both directions from the seat of fire, causing different kinds of damage to people. Anyway, underground fire causes complicated results, which is preventing factor for life rescue and evacuation, creating difficulties for firemen and life rescue crew. Analysis of the critical speed, which is necessary for the effective management of combustion products, has been made for tunnel fires with high heat release rate. The characteristic changes in the critical Froude number in the work are presented in accordance with the critical speed. Particularly, it was noted that the formula determining the critical speed requires knowledge of the average smoke temperature, while the formula for calculating the last value includes the value of the required critical speed. In order to overcome this, Froude’s critical number Frc=4.5 has been introduced, which is not the way of solution, as it directly means constant critical velocity for the fire of any power and accordingly, does not correspond to experimental data.

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“…The results of simultaneous heat and moisture transfer in the tunnels were investigated previously [24,25].…”

Section: Positive and Negative Directions Of Ventilation Streammentioning

confidence: 99%

Critical velocity analysis for safety management in case of tunnel fire

Lanchava

Iliaş

2020

MATEC Web Conf.

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“…Fires in transport tunnels were studied in various aspects: characterization of underground fires and smoke propagation scenarios [9][10][11][12][13][14][15][16][17][18], issues of temperature distribution and propagation in tunnels, as well as non-stationary and quasi-stationary heat exchange processes between the rock mass and ventilation flow [19][20][21][22][23], influence of the tunnel gradient on back layering length in terms of natural ventilation [11,24,25], propagation of smoke and toxic combustion products in the direction opposite to the movement of ventilation flow [18,[24][25][26], dynamics and scenarios of fire development under the ground [26][27][28], theoretical and experimental studies of critical velocity [29][30][31][32][33][34][35][36], and impact of piston effect of moving transport on ventilation [37].…”

Section: Introductionmentioning

confidence: 99%

Badanie efektu dławienia w pożarze tunelu

Lanchava,

Bezhanishvili,

Javakhishvili

et al. 2024

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As per the emergency ventilation strategy, air velocity of 3 m/s in case of the longitudinal ventilation is sufficient for smoke control in all fire conditions. Numerical experiments were carried out with FDS software to estimate the numerical value of the critical velocity. Numerical models were realized in 0-6% slope tunnels with a 1% step for 5, 10, 20, 30 and 50 MW fires for four types of fuel: gasoline, diesel fuel, oil and firewood. The paper notes that the dynamic pressure induced by a strong fire is much higher than the static pressure of tunnel jet fans. As a result, following the algebraic summation of positively-directed ventilation flows and the negatively-directed flows induced by fire, an intense back layering occurs, which casts doubt on the suitability of the specified emergency ventilation strategy when designing the fire ventilation. The critical ventilation speed of 3 m/s cannot cope with the traction caused by fire, expressed by the ascending movement of the high-temperature and low-density combustion products. The paper discusses the numerical modelling results with an adiabatic underground heat exchange model and presents typical tunnel fire modelling plans, which correspond to an inclined tunnel for ascending and descending ventilation flows as well as a horizontal tunnel. The article gives the regularities obtained by the numerical models of changes in the variables of average air temperature and density, average carbon monoxide, average carbon dioxide and soot concentrations. According to the emergency ventilation strategy, critical velocity is an important value and a major determinant of back layering prevention in sloping tunnels. Although many papers have been devoted to this problem, the obtained results differ much. The present paper shows that strong fires induce much greater dynamic pressures than the static pressures of the tunnel jet fans are. Consequently, the flows caused by these forces, as they move in different directions, following their algebraic summation, cause a strong back-layering in case of positive ventilation flows, i.e., when the ventilation flow is descending and the fire seat is found at a lower point compared to the air supply portal. The new results can be used to develop fire ventilation plans as well as life-saving and emergency control solutions in the operating tunnels for personnel and rescuers.

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“…According to the building norms and regulations applicable in our country, tunnels less than 150 m long are ventilated only by natural traction; tunnels with lengths ranging from 150 to 400 m should also receive natural traction, but its sufficiency should be proven by a relevant assessment. Tunnels longer than 400 m need a mechanical ventilation system (Lanchava & Javakhishvili, 2021;Lanchava & Ilias, 2020;Lanchava, 1986). England has similar regulations: mechanical ventilation is not required for tunnels less than 400 m long, while according to the German RABT Standard, tunnels less than 700 m long do not require mechanical ventilation and are mandatory for tunnels longer than 700 m.…”

Section: Introductionmentioning

confidence: 99%

Some Questions about the Safe Operation of Short Road Tunnels

Lanchava

2024

ggj

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Heat and mass exchange in newly driven mine workings

Cited by 8 publications

References 1 publication

Critical velocity analysis for safety management in case of tunnel fire

Critical velocity analysis for safety management in case of tunnel fire

Badanie efektu dławienia w pożarze tunelu

Some Questions about the Safe Operation of Short Road Tunnels

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