Blasting Conventional or drill-and-blast excavation Conventional excavation using shotcrete consolidation is a very flexible excavation method. It is suitable for difficult, varying rock mass conditions, for different cross-section sizes and for complex cross-sectional geometries. Due to the complex excavation requirements, some sections of the main tunnels and exploratory tunnel, as well as the two connecting tunnels, all of the lateral access tunnels, ventilation and logistics caverns, cross-connecting tunnels, emergency stops and by-passes are being excavated using the so-called conventional excavation method, meaning by blasting (full and partial surface breakout) with shotcrete consolidation. The stages for drilling and blasting are predetermined. The blast holes are drilled at first, then loaded with explosives and finally, the explosion takes place. Once the spoil has been removed, a process known as mucking, tunnel support is applied in the form of shotcrete, anchors, lattice arches and reinforcement mats. After one blasting cycle is complete, the process starts all over again. During the construction of the Brenner Base Tunnel blasting takes place every three to six hours depending on the geological composition of the rocks. Unlike in Austria, in Italy the entire cross section of the tunnel was blasted all at once. Bench excavation Crown excavation Crown stabilization Mobile concrete spraying machine Excavation drilling jumbo Drilling jumbo Wheel loader Fresh air supply Rock anchor Dumper Concrete mixer truck Various excavation methods are used to drive the Brenner Base Tunnel forward, using special machines and explosives. The choice of excavation method depends on the geology of the mountain, on geotechnical findings and forecasts, and on construction logistics and economic considerations. The length of the route to be excavated and the available construction time both influence the choice of excavation method. So some sections of the tunnel are excavated by drilling and blasting whilst others are built using mechanical construction methods, i.e. with a tunnel boring machine (TBM). 16 BRENNER BASE TUNNEL
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