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Today more and more underground facilities and tunnels are built. Fires in tunnels and underground facilities can lead to catastrophic consequences for users and owners. Fires in tunnels are complex phenomena and are in many cases difficult to calculate or simulate.  Therefore the knowledge and design must primarily be based on information obtained from full and model scale tests.

The convective air flow is crucial in an emergency situation but can also affect other installations such as fans. The thesis focuses on these two research areas.

The stratification of the convective flow (temperature stratification) and the smoke is a very important part of the safety design. There are methods available to determine the temperature stratification. Based on a method proposed by Newman previously performed fire tests, both in full and model scale were analyzed. One aim is to obtain simple expressions for hand calculations of the temperature conditions inside a tunnel in case of a fire. The thesis presents a summary of simplified semi-empirical expressions for calculations of fire phenomena in tunnel fires. A key factor for the resulting air velocity in the tunnel is the external wind effects. Based on previous work and a new study, semi-empirical expressions for calculations of wind effects in tunnels are presented.

The thesis also presents detailed studies of air motion conditions in and around various tunnel entrances at different wind directions and pressures. Analyses were carried out with different pressure measurement and visualization experiments.

The following results are presented in the thesis:

• Reasons and arguments for a risk-based approach for fire design of tunnels

• A compilation and analysis of full-scale and model tests from a temperature and smoke stratification perspective according to a method proposed by Newman

• A revised correlation model for temperature calculations based on two full-scale experiments and a model test

• Simplified correlations and graphs for the calculation of external wind effects in tunnels

• Enhanced analysis of wind effects in tunnels