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.