Friday, June 2, 2023

Power project marks another milestone

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Despite recent news about time and cost blowouts, the Snowy 2.0 pumped-hydro mega project has achieved another important construction milestone, with a second tunnel excavation completed at Lobs Hole.

The 2.93-kilometre emergency, cable and ventilation tunnel (ECVT) has been excavated and fully lined with 13,140 locally-manufactured concrete segments by tunnel boring machine (TBM) Kirsten.

This achievement follows the excavation of the adjacent main access tunnel (MAT), which was completed in October 2022.

Snowy Hydro CEO, Dennis Barnes, said Snowy 2.0 was continuing to make solid progress with around six kilometres of tunnelling by TBMs completed and drill and blast excavation of the power station cavern about to start.

“We are extremely pleased the ECVT excavation has been completed and the whole project team is excited to be moving into the next critical phase of construction,” Mr Barnes said.

“Our huge power station cavern will be located about 800 metres underground and will be one of the largest and deepest in the world.

“We are also using drill and blast methods to construct cross passages linking the ECVT with the MAT.

“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 per cent incline using an 11-metre diameter TBM is without precedent internationally,” Mr Barnes added.

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.

The milestone has been offset by one of the TBM’s being stuck underground since December 2022.

Mr Barnes has acknowledged that TBM Florence may be stuck for “weeks or months” longer.

He said significant efforts were being made to extricate the 2,000-tonne machine, which triggered a sinkhole when it struck trouble 70 metres into a 17-kilometre journey.

Part of these efforts would include constructing a slurry machine that can “liquefy” the soil in front of the borer, making its passage forwards easier.

“Prior to the financial investment decision there was in the order of $100m spent on geotechnical surveys,” Mr Barnes said.

“So we feel we have good coverage of the site. We are obviously looking at ways to mitigate the schedule delay.” 

Corryong Courier 25 May 2023

This article appeared in the Corryong Courier, 25 May 2023.


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