Raising Collabos' Safety Standards

This article describes the method of excavation for the upgrade of the Traffic Infrastructure Authority of Catalonia, Spain’s 1.9 km long Collabos tunnel that will outfit the structure with an emergency exit tunnel as per the recent safety requirements established in Europe. This tunnel, which was constructed by TBM in order to close the distance between the two tunnels to 15 meters, is connected to the main tunnel by cross-passage every 250 meters. A hard rock gripper tunnel boring machine (TBM) was used that was previously used with a smaller cutterhead for a project in Switzerland. As the tunnel had a shallow gradient, the contractor opted for a traditional mucking system. The year-long project went as anticipated, with progress being slowed throughout fault zones. The article also describes the construction of the 6 cross-passages that were subcontracted to an Austrian company which used a raised boring unit with a special centering tool and a head modified with scrapers. The article closes with a description of the advantages and disadvantages for the machines utilized in this excavation (namely a TBM in lieu of a blast method and a horizontal raise boring).