Description
In a road tunnel project in Australia currently under construction, the tunnel consists of broadly two fire separated tubes, with each tube typically having three lanes of traffic. Cross passages are provided 120m centres for evacuation to a non-incident tunnel and access for fire brigade intervention.
Part of the tunnel, approximately 1.5km long, will be constructed with Tunnel Boring Machines (TBMs) with a crown height of about 10m above the carriageway. The excavation path comprises a 200m section of soft ground, resulting in considerable risk when constructing cross passages. A risk analysis was undertaken to determine the benefit of increased cross-sectional area and obvert above the road level inherent in the TBM tunnel design. This would inform the fire engineering strategy in areas of soft-ground conditions to offset any increase in risk to construction personnel.
