A tunnel can ride out a fire without collapsing (or even critical visible structural damage), but a question whether it is safe for operations, and what is its long-term residual fire resistance remains. With repair bills being in high seven-eight figures, this is more than just a theoretical question... In this episode we dig into the hard middle ground of fire damage post mild/large fires, and cover where modeling and fire science can help reducing the uncertainty and guiding decisions. With Professor Negar Elhami-Khorasani from University at Buffalo, we map how ventilation settings, tunnel slope, and fuel push temperatures into either safe or punishing regimes, and why spalling can turn a survivable event into a structural headache.

We break spalling down to first principles—vapor pressure, thermal gradients, and restraint—then translate that into a practical method: update the section as concrete “disappears” so the thermal boundary moves and heat penetrates realistically. From there, we track damage you can act on: concrete volumes beyond 300°C, steel temperatures that risk incomplete recovery, and bond loss that forces major repairs. Just as important, we model through cooling, when heat keeps migrating and residual capacity sinks. The result isn’t a guess; it’s a bounded map of what to replace and why.

We also take on the tactical questions that matter: How long would an extreme fire need to threaten collapse, given different soils and depths? What’s the real value of polypropylene fibers in high-strength mixes? How should owners structure a fast, post-fire workflow—quick checks for reopening within days, followed by a deeper, simulation-informed durability plan? By pairing observed spalling and known operations with targeted heat transfer and mechanical analysis, you can reconstruct the event, communicate risk clearly, and spend repair budgets where they return the most resilience.

If you care about structural fire engineering, tunnel safety, spalling mitigation, and performance-based design that reduces downtime, this conversation delivers a roadmap you can use.

Further reading - recommended papers by Negar Elhami-Khorasani and her team:

Structural fire behavior of tunnel sections: assessing the effects of full burnout and spalling effects

Numerical modeling of the fire behavior of reinforced concrete tunnel slabs during heating and cooling

Fire Damage Assessment of Reinforced Concrete Tunnel Linings

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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

Welcome to another fire fundamentals episode! Today we dig into how to place a fire in a model so results reflect real physics. From plume inputs to FDS burners, we show where HRRPUA, radiative fraction, and D* make or break smoke your calculations. Things considered in this episode:

• why defining the design HRR is separate from placing the source
• what a flame is and why we cannot resolve its chemistry
• plume models compared by inputs: perimeter, Q, Qc
• entrainment, virtual origin, and effective diameter
• realistic HRRPUA ranges for building-scale fires
• radiative vs convective fractions and why they matter
• zone model linkage to plumes for smoke control
• volumetric smoke and heat sources for CFD: volume, placement, and limits
• fuel-based fires in CFD and oxygen constraints
• growth modeling via area expansion vs flux ramping
• soot yields, heat of combustion, and visibility
• D* and meshing guidance for credible resolution
• why predictive fire spread modelling for design use does not really exist...

Resources, resources!

• G. Vigne et al. "Review and Validation of the current Smoke Plume Entrainment Models for Large-Volume Buildings"
• W. Węgrzyński & M. Konecki "Influence of the fire location and the size of a compartment on the heat and smoke flow out of the compartment" - (this is a paper from my PhD where I explain the concept of volumetric heat source)
• M. Bonner et al. "Visual Fire Power: An Algorithm for Measuring Heat Release Rate of Visible Flames in Camera Footage, with Applications in Facade Fire Experiments"
• Episode 100 - Smoke plumes! That was a fun one.
• G. Heskestad "Fire Plumes, Flame Height, and Air Entrainment" from SFPE Handbook (also the source of the overlayed image on the cover showing range at which fires exist)

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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.

Welcome back to Fire Fundamentals! Today with prof. Ali Rangwala from WPI and dr Lorenz Boeck from Rembe and WPI we take the world of explosion protection engineering.

In this episode we touch:

• distinguishing fires and explosions by time scale and damage mode
• taxonomy of explosions by energy density and deposition time
• hybrid mixtures in coal mines and turbulent burning velocity
• severity metrics for gases and dust deflagration index for reactivity
• explosion sphere testing, ignition positioning, and model limits
• ignition sensitivity minimum ignition energy and hot surface risks
• prevention via ventilation, inerting, and ignition control
• protection through deflagration vents, isolation, and external hazards
• pressure vessel bursts, inspections, and rupture disks
• transport scenarios vapor clouds and BLEVEs with fireball correlations

We also delve into future directions for explosion research:

• emerging risks hydrogen, BESS, ammonia, and layered defenses
• space and microgravity impacts on dust and flammability

Check out the XPE programme at WPI, and find more informations on how to enroll at: https://www.wpi.edu/academics/study/master-science-explosion-protection-engineering

I have also received some good listening material, that you could follow up with:

• A podcast done by Ali's PhD student, Hannah Murray and Prof. Stephen Kmiotek who is the co director of XPE. This was done by WPI and the link is : https://www.wpi.edu/listen/wpi-podcast/e18-explosion-protection-engineering-hannah-murray-explosion-protection-engineering-phd-candidate
• There is one more podcast that was more focused on dust explosions. This was done by Dust Safety Science, by Chris Cloney and also explains the program. In this its Prof. Kmiotek and Ali: https://dustsafetyscience.com/explosion-protection-engineering-program/

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The Fire Science Show is produced by the Fire Science Media in collaboration with OFR Consultants. Thank you to the podcast sponsor for their continuous support towards our mission.