Fire tests of cut and cover tunnel roof segments at positive moment region

Arsava, Kemal Sarp
The most important issue during a tunnel fire is safety of human life. The tunnel fire structural research and investigations have gained more importance in the last decade but studies show variable results depending on the concrete quality and tunnel design fire. For instance, a certain type of concrete with high moisture content can tend to explode in the first 10-15 minutes of fire with rapid increase of heat release rate. A sudden collapse of the tunnel roof during the fire is unacceptable. Especially in Netherlands, the possible sagging of cut and cover tunnel roof is undesired and prevention systems are applied. The main purpose of this research is to investigate fire response of the positive moment region of cut and cover tunnel roof through an experimental and analytical program without use of any protection. In this context a standard one cell rail road cut and cover tunnel has been designed for loads of backfill, lateral earth pressure and self weight. The typical concrete cover used in Turkish railroad tunnels is 6 centimeters. Four pairs of representative sample tunnel roof segments have been manufactured and only one segment out of each pair are tested under 2 hours extreme design tunnel fire in a furnace. Out of these four types, two types have been internally pre-stressed to simulate the internal loads at the positive moment region of the tunnel roof. Four pairs of sample segments are simply supported during the static load test and static load is applied at the mid-span to measure the difference in the post-fire structural performance. Compressive strength of concrete, tensile strength of reinforcing bars, electron microscope evaluation of concrete, moisture content of concrete are recorded during the test program. A finite element based solution is developed to simulate the results of static load tests. Post-fire structural performances of burnt segments are observed to be not much different than the unburnt segments.
Citation Formats
K. S. Arsava, “Fire tests of cut and cover tunnel roof segments at positive moment region,” M.S. - Master of Science, Middle East Technical University, 2011.