Abstract: Abstract: In order to solve the smoke exhaust problem of extra-long subsea tunnel in fire, a ventilation scheme using service tunnel and cross passage to assist air supply is proposed. In this paper, fire dynamics simulation software (FDS) is used to establish the tunnel fire ventilation model. The technical parameters of the ventilation system are determined by studying the control effect of the air volume in service tunnel and the number of cross passage openings on the fire smoke. As a result, in the fire scenario, when the longitudinal ventilation wind speed in the accident tunnel is 2 m/s, three cross passages in upstream of the fire source are opened, and 1.3 m/s longitudinal ventilation wind speed is applied at both ends of the service tunnel, the smoke can be controlled on one side of the fire source without affecting the safety evacuation of personnel. The research shows that it is feasible in theory to control the spread of fire smoke in extra-long subsea tunnel by using cross-passage assisted ventilation scheme.

Key words: Key words: fire, smoke control, cross passage, FDS