Numerical Study of Large-Scale Fire in Makkah’s King Abdulaziz Road Tunnel

Tunnel fires are one of the most dangerous catastrophic events that endanger human life. They cause damage to infrastructure because of the limited space in the tunnel, lack of escape facilities, and difficulty that intervention forces have in reaching the fire position, especially in highly crowded areas, such as Makkah in the Hajj season. Unfortunately, performing experimental tests on tunnel fire safety is particularly challenging because of the prohibitive cost, limited possibilities, and losses that these tests can cause. Therefore, large-scale modeling, using fire dynamic simulation, is one of the best techniques used to limit these costs and losses. In the present work, a fire scenario in the Makkah’s King Abdulaziz Road tunnel was analyzed using the Fire Dynamics Simulator (FDS). The effects of the heat released per unit area, soot yield, and CO yield on the gas temperature, radiation, concentrations of the oxygen and combustion products CO and CO2, and air velocity were examined. The results showed that the radiation increased with the heat released per unit area and the soot yield affected all parameters, except the oxygen concentration and air velocity. The CO yield significantly affects CO concentration, and its influence on the other studied parameters is negligible. Moreover, based on the validation part, the results proved that FDS have limitations in tunnel fires, which impact the smoke layer calculation at the upstream zone of the fire. Therefore, the users or researchers should carefully be concerned about these weaknesses when using FDS to simulate tunnel fires. Further comprehensive research is crucial, as tunnel fires have severe impacts on various aspects of people’s lives.

Application of numerical modeling to assess the influence of the longitudinal slope in a road tunnel on the fire hazards spread

Рассмотрено влияние продольного уклона автодорожного тоннеля на распространение в нем опасных факторов пожара при возникновении загорания. Для оценки этого влияния использован полевой метод моделирования. Проведен анализ полученных результатов. Сделан вывод о том, что «классическое» понимание картины пожара, основывающееся на принципе «чем больше уклон тоннеля, тем быстрее происходит блокирование», при определенных условиях может не соответствовать действительности. При этом большое влияние на результат расчетов может оказывать постановка граничного условия постоянства давления. One of the important issues in the design and construction of tunnels is to ensure their fire safety. To take into account the characteristics of a particular object and make decision on its effective fire protection, it is necessary to study the influence of various factors on the dynamics of a possible fire. Conducting field tests in this case is expensive and time-consuming. Therefore, one of the most effective methods in this case is numerical modeling. In this paper there is considered the issue of the influence of the longitudinal slope value of a road tunnel on the dangerous factors spread in case of fire. The assessment was carried out by simulating a fire in a model tunnel using the field method. A model tunnel of rectangular cross-section was chosen for conducting numerical experiments. The SOFIE software package was used to implement the model. To evaluate the results obtained there were created the fields of optical smoke density in the central longitudinal section at various time points. This dangerous fire factor is the determining factor because it reaches critical values most quickly. As a result of calculations in the work there was established the influence of the tunnel slope value on the fire hazards spread. It is found that the nature of fire hazards spread in a tunnel without a slope significantly differs from their propagation pattern in an inclined tunnel. If there is a slope, the blocking of tunnel sections (escape routes) up the slope during the first minutes of fire occurs much faster than down, so it is preferable to evacuate people in case of an emergency down the slope. Under certain conditions the principle “the greater the slope of the tunnel, the faster the blocking occurs” can be untrue. At the same time, the obtained result depends on the setting of the boundary condition of pressure constancy during the calculation and can differ from the real fire performance, however, in general, it is not an underestimation of fire danger and can be used in engineering calculations.

Noninvasive Passenger Detection Comparison Using Thermal Imager and IP Cameras

Many modern vehicles today are equipped with an on-board e-call system that can send information about the number of passengers in the event of an accident. However, in case of fire or other major danger in a road tunnel, it is very important for rescue services to know not only the number of passengers in a given vehicle that has an accident and called help via e-call but how many people are in the tunnel in total. This paper deals with the issue of passenger detection and counting using the TPH3008-S Thermal camera and the VIVOTEK IP7361 IP Cameras noninvasively, i.e., the cameras are placed outside the vehicle. These cameras have their limitations; therefore, we investigated how to improve conditions and how to make detection better for future work. The main goal of this article is to summarize the achieved results and possibilities of improvement of the proposed system by adding other sensors and systems that would improve the final score of passenger detection. The experimental results demonstrate that our approach has to be modified and we have to add additional sensors or change methods to achieve more promising results. The results, findings and conclusions might be later used in tunnels and highways and also be applied in telematics and lead to better, safer road transport and improvement of existing tunnel systems sustainability by utilizing resources in a smarter way.

FDS simulation of smoke backlayering in emergency lay-by of a road tunnel with longitudinal ventilation

This paper investigates smoke movement and its stratification in a lay-by of a 900 m long road tunnel by computer simulation using Fire Dynamics Simulator. The lay-by is located upstream of the fire in its vicinity. The influence of lay-by geometry on smoke spread is evaluated by comparison with a fictional tunnel without lay-by. Several fire scenarios with various tunnel slopes and heat release rates of fire in the tunnels without and with the lay-by are considered. The most significant breaking of smoke stratification and decrease of visibility in the area of the lay-by can be observed in the case of zero slope tunnel for more intensive fires with significant length of backlayering. Several other features of smoke spread in the lay-by are analysed as well. The parallel calculations were performed on a high-performance computer cluster.

Thermo-Mechanical Behavior of Fire Protection Boards

In the course of the repair and fire protection upgrading of an approx. 1100 m long road tunnel in Hamburg, the eleven crossings of fire protection channels were covered with sheet steel to prevent the nesting of pigeons. In this context, the mechanical strains that may occur in the event of a fire had to be determined. In particular, it was necessary to clarify which mechanical loads would result from relative movements between the substrate (fire protection board) and the cover sheets due to their different thermal expansion in case of fire. For this purpose, the thermal behavior of the CSH fire protection board was determined by means of simultaneous thermal analysis and dilatometry, and the mechanical and thermal behavior of the composite construction was studied. The studies revealed that due to the facts that thermal expansion of the both materials and due to the softening of the fire protection panel the restraint that is generated by the screwed-on perforated plate in the vicinity of the screw shafts remains low during thermal loading. As a result, the top plate does not crack or break off, which means that screwing on the perforated steel sheets not negatively affects the fire protection of the panels.

Numerical simulation of fire in road tunnel. Selection of calculation grid

Рассматривается вопрос выбора расчетной сетки при моделировании пожара в тоннеле с помощью полевого метода и проводится оценка возможного влияния размеров ячеек сетки, а также граничного условия постоянства давления на результаты расчета. Выполнено моделирование пожара для четырех размеров расчетной сетки. Обоснована возможность применения наиболее грубой из используемых сеток с точки зрения инженерных расчетов, в том числе с оговоркой относительно постановки граничного условия. The issue of fire safety of road tunnels is currently an urgent task. Road tunnels are usually not standard typical facilities, but the unique structures. Therefore, it is necessary to study the influence of various parameters on the development of fire in order to take into account the characteristics of a particular object and make decisions on its effective fire protection. Implementation of field tests in this case is expensive and time-consuming. In this regard, numerical modeling is one of the most effective methods of such research. Field models are the most common and currently used for numerical calculations. These models are based on the numerical solution of the system of conservation equations for small control volumes of the calculation grid. This paper examines the issues of selection the calculation grid when modeling a fire in tunnels using the field method is considered and the possible influence of the size of the grid cells is estimated. The mathematical model used in this work is based on a set of differential equations of hydrodynamics, heat transfer, as well as the equation of conservation of the masses of components. Four computational grids were selected for a horizontal (without slope) model tunnel to determine the optimal cell size. As a result of conducted calculations it was established the following: the size of calculated grid is not fundamental for the initial stage of the fire; the use of smaller grid may be preferable at further development of fire, accompanied by increase of combustion capacity to the maximum; the maximum temperature values, especially in the far sections, are obtained on the coarsest grid. The use of such a grid for estimated engineering calculations can be allowed.