The Snowy 2.0 pumped-hydro mega project has achieved another important construction milestone, with a second tunnel excavation completed at Lobs Hole in the Snowy Mountains.  

The 2.93-km in length and 10 m internal diameter emergency, cable and ventilation tunnel (ECVT) has been excavated and fully lined by TBM Kirsten with 1,460 concrete rings (9 precast segments per ring manufactured locally in Cooma). This achievement follows the excavation of the adjacent main access tunnel (MAT), which was completed in October 2022.  

Now around 6 km of tunnelling by TBMs has been completed for Snowy 2.0 and drill & blast excavation of the power station cavern - about 800 m underground - is going to start. 

The 5 cross passages linking the ECVT with the MAT are being built using the drill & blast method.  

Meanwhile TBM Kirsten, which is setting a global standard in TBM technology, is being modified to carry out another very specific task – to excavate the inclined pressure shaft and line it with specially-designed and locally manufactured concrete segments.  

The shaft is 1.45km long and excavating a segment lined tunnel of this length at a very steep 47% incline using an 11-m diameter TBM is without precedent internationally.  

Modifications to Kirsten include altering the levels of the TBM’s tanks and mechanical equipment so they remain horizontal when travelling up the incline, and converting the walkways into steps and ladderways.   

Also being installed is a screw conveyor to extract excavated rock from the cutterhead to a sandwich conveyor system with face-to-face rubber belts that help constrain the crushed rock so that it can be transported down the steep slope without spillage.  

Additional plant and equipment will also be installed in the ECVT tunnel to support the excavation activities including; an overhead crane, a conveyor transfer station, monorail manrider for personnel access and rack and pinion mechanism for plant access to the TBM. 

Click here and au/38 for further information in the tunnelbuilder archive. Visit https://www.snowyhydro.com.au/ . 22/23.