Rigorous understanding of tunnel fire attributes and behavior of concrete at elevated temperatures are indispensable for conducting a numerical simulation of tunnel linings exposed to fire. One of the main feats of tunnel fires is, unlike cellulose fires, temperature of these fires quickly ascends to its zenith, which is higher than conventional cellulose fire temperature. Higher peak temperature in conjunction with rapid heating rate causes spalling in the tunnel linings, which is triggered by excess vapor pressure in concrete pores generated from evaporation of moisture in concrete. Apart from vaporization of moisture, multiple simultaneous physiochemical processes (dehydration/hydration, desorption/sorption, α-β transformation of quartz, decarbonation) take place in concrete when it gets heated. Modelling of a tunnel fire using a commercial finite element tool without taking into account of these physiochemical processes and latent energy associated with the phase changes will result in inaccurate prediction of the results. Thus, the behavior of concrete tunnel liners in extreme fire conditions and relevant material parameters required for numerical simulation are presented in this paper.
|Number of pages||9|
|Journal||Tunnelling and Underground Space Technology incorporating Trenchless Technology Research|
|Early online date||2 May 2022|
|Publication status||E-pub ahead of print - 2 May 2022|
Bibliographical noteFunding Information:
Meanwhile other countries started developing their own standard fire curves. In 1979, after a devastating accidental fire in the Velsar tunnel, TNO center of Fire Safety of Netherlands ( TNO, 1998 ) proposed the RWS (Rijkswaterstatt) fire curve which simulates the burning of a 50 m 3 petrol tanker of 300 MW fire for two hours. The RWS curve was initially proposed on the Dutch experience of tunnel fires which was supported by the full scale fire tests conducted in Sweden’s Runehamar tunnel under UPTUN project of European Commission ( EFNARC, 2006; Jong, 2020; Lönnermark, 2005 ). RWS curve is by far the most extreme fire curve being used, where the temperature quickly ascends to 1200 °C and reaches up to 1350 °C at 60 min within 120 min of total fire exposure.
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- Behavior of concrete at elevated temperature
- Fire curves
- Mechanical properties
- Numerical simulations of tunnel fire
- Thermal properties
- Tunnel fire