ABSTRACT
This paper compares the life cycle cost (LLC) and safety level of a single bore bidirectional (SBB) tunnel including semitransverse ventilation and a parallel escape adit (PEA), with a twin bore unidirectional (TBU) tunnel of the same length. The tunnel’s length is arbitrarily selected 3800m. The design fire for the SBB tunnel is selected 100MW; the civil works of the SBB tunnel also include a 400m high ventilation shaft with a vent fan room at its top. Two traffic cross sections have been examined, the first including a clearance borderline (CBR) 7,5m wide and 4,5m in height, and the second a CBR 8,5m wide and 5m in height. A PEA either for pedestrians or for emergency vehicles has been examined. LCC costs have been included reinvestment cost, operation & maintenance cost and accidents cost. Within the design life of the structure and under the considered assumptions, the SBB tunnel has been found becoming more expensive than the TBU tunnel in all cases.
