Phase 1: Isarco river underpass construction lot
4.2 km of main tunnels, 1.8 km of connecting tunnels
The first construction phase of the project consists on the construction of four shafts, 20-25 metres deep, to access the rock faces of the Isarco River Underpass. Furthermore, it includes the excavation of the access tunnel on the right side of the valley using drill and blast, and of part of the main tubes and the connecting tunnels, to be built with the drill and blast method.
This part of the project presented several challenges:
• Due to the proximity of the Fortezza town, the ground vibration had to be under the authorized levels.
• Deliveries on time (24/24 and 7/7) because there was no explosive deposit.
• High performance explosive for the breaking of the hard rock (granite).
• For the smooth blasting use an insensitive explosive to shocks.
• Safety attivation of the detonators Rionel MS & LP.
Premex 300 Profil was used to help the customer overcome the problems related to finding the detonating cord after the shots. This is a special product designed for pre-splitting and contour blasting. It has rigid cartridges in plastic tube with special cap self-centering. The cartridges have dimension 25x460 and weigh 0,250 kg/cad (100 cartridges). The priming of these cartridges is given by a Riodin booster.
To ensure the safety of the operation, the RIONEL MS & LP detonator was used, together with Rionel SCX connectors. This kind of connector has guaranteed security to activate all detonators of blasts.
Additionally, and in order to reduce vibrations to nearby structures, more detonators were used helping to reduce the MIC (Max Instant Charge). And in order to measure and control the operation, there were a continuous seismic monitoring of it.
Phase 2: Mules 2-3 construction lot
39,8 km of the main tubes and 14.8 km of the exploratory tunnel will be excavated
This lot reaches from the construction lot “Isarco river underpass” up to the border with Austria. In the course of a 7-year construction period, 39,8 km of the main tubes and 14.8 km of the exploratory tunnel will be excavated, including the emergency stop in Trens and its access tunnel as well as the bypasses which connect the main tubes every 333 m. A total of approximately 65 kilometers of tunnels will be excavated. Once this construction lot is finished, all excavation activities in the Italian project area will be complete.
This part of the project presented a lot of challenges:
• Due to the proximity of the exploratory tunnel, the ground vibration had to be under the authorized levels.
• Deliveries 24/24 and 7/7 to ensure to all the tunnels a continuous supply of explosive.
• Different kind of explosive for different kind of rock.
• Provide the best possible profile of the excavation wall.
Different kind of rock needs different kind of explosive
During the tunnel excavations on the Italian side of the work, the team must deal with many different types of rocks. In the south part of the tunnel there is a very hard granite, which makes necessary to use an explosive with good performance like a high detonation speed and good quantity of energy.
For that MAXAM has its RIODIN HE 40x400. This technology was used in 60% of the works while cartridged emulsions were applied in the remaining 40%.
On the other hand, rock formations of the type schist were found on the north part. For this type of rock the RIOHIT XE 40x600 was preferred under careful analysis by MAXAM experts.