The SELI joint venture has completed tunnel excavation on the Passirio (Val Passiria) small hydro project in Italy with the breakthrough of the 3.7m diameter double shield universal (DSU) TBM for the headrace drive.
Seli modified a Wirth double shield for the 5,885m long headrace tunnel excavation, which took 12 months to complete. Average advance during the bore was 500m per month, though inflows up to 400 l/s slowed progress at times.
Geology along the alignment is comprised of gneiss and micaschist. The TBM was fitted with 17” cutters, has a maximum cutterhead thrust of 5,280kN and total drive power of 1,120kW.
The headrace – which was the only TBM-driven tunnel on the project – has an internal diameter of 3.1m. The segmental lining (4 trapezoidal) is 200mm thick and rings are 1.1m long.
Seli and local JV partner Edilmac were awarded a two-year contract for the works in the third quarter of 2006, valued at US$30.4M in 2006 prices, US$36.6M in current prices. The client is Enerpass AG.
Other tunnelling works on the project included 113m and 51m long access tunnels, excavated by drill and blast. The JV also excavated a 48m deep shaft by raise bore, which was also lined with concrete segments.
Seli holes through at Passirio Seli holes through at Passirio
