Behavior of Underground Open Fires in a Full-scale Test Gallery

Abstract

In order to investigate the characteristics of underground open fire, a series of experiments have been carried out by using a 400m long test gallery with a cross section of 5.4 m² and timber sets arranged as in practical roadways. Also the scale effect on the spread behavior of fire was studied on the basis of the experimental results by the small and the full scale galleries.
The results obtained are summarized as follows;
(1) When the timber is exposed to the ignition source emitting heat more than 780 kW/m³, the fire develops into the fuel-rich condition, expanding the fire zone to the maximum length where most oxygen is consumed.
(2) The fire spread rates and the fire zone lengths in the full scale gallery are both proportional to the air velocity.
(3) Types of timbering also influence the behavior of fire. The fire temperatures in arch lined timbering are lower than those in three piece timber sets. Fires of arch lined timbering tend to become the oxygen-rich condition in which large quantity of oxygen remains in the fume.
(4) Scale effects are observed between the model and full scale experiments. Supposing fuel and ventilation conditions are the same, the fire spread rate of timber zone is proportional to the ratio of gallery dimension to timber dimension, and the fire zone length is proportional to the gallery dimension.
(5) A calculating method for estimating the fire spread rate and the fire zone length of underground open fires is proposed, the scale effect on fire spread characteristics and the change in ventilation being taken into account.