July marked an exciting milestone for Snowy Hydro, Snowy 2.0 and Future Generation Joint Venture - FGJV with the relaunch of TBM Lady Eileen Hudson - one of the mega project's three TBMs - at Talbingo adit for her second tunnel excavation: click here for a video.
TBM Lady Eileen Hudson was the first machine to start tunnelling on the pumped-hydro mega project, the first to complete a tunnel and is now underway on her second tunnel excavation.
The machine will excavate the 6km tailrace tunnel to connect Talbingo Reservoir to the underground power station complex. Water used to generate 2,000 megawatts of power from Snowy 2.0 will flow out of the tailrace tunnel. Water also enters this tunnel when the power station is pumping.
After completing the 2.8km main access tunnel (MAT) in 2022, it has been a big task to disassemble and safely extract TBM Lady Eileen and reassemble her with new components before commissioning. The new 378-t cutterhead is made up of 70 cutting discs each weighing 290 g that will excavate the varying geology of the 11-m diameter tunnel. The conveyor stacker, grout batch plant, and chiller plant were also relocated from the MAT portal to the Talbingo adit.
The TBM - 137 m in length and weighing 2,300 t - will install using the segment erector, segment feeder, segment cranes, and sophisticated grouting system all onboard it more than 27,000 concrete segments manufactured at the Polo Flat, Cooma, precast facility to line the tailrace tunnel.
The TBM is also equipped with a guidance system that provides data to the machine’s pilot, to the nearest millimetre.
Local parish priest Father Mark Croker blessed the TBM at an onsite ceremony with many Snowy 2.0 workers in attendance. The machine was then switched on and began cutting the rock face. This is the fourth TBM launch for Snowy 2.0 and a major achievement for the Snowy Scheme expansion project.
Meanwile successful ground stabilisation works and construction of a slurry treatment plant at Tantangara have been carried out by Snowy 2.0 teams prior to TBM Florence being able to restart excavation of the headrace tunnel.
Final commissioning tests are underway for the onsite slurry plant that means the dual-mode machine can switch from open excavation to a closed, pressurised mode. This method of excavation will enable stable excavation and efficient progress through softer ground conditions when required.
A significant testing regime has confirmed grouting and stabilisation of the loose material around TBM Florence has been effective.
Additional stabilisation continues from the surface to solidify loose material above the machine and directly in front of the TBM cutterhead and the rock mass the machine is just short of.
Rotations of the cutterhead and minor advances of TBM Florence are carrying out to ensure the machine is correctly positioned for final commissioning and to confirm the ground support activities are working.
The contractor is working with NSW departments on environmental approvals for remediation of the surface depression above TBM Florence and to provide assurance that this will not reoccur.
The plan is likely to go on public display in the coming weeks.
The slurry treatment plant will process and separate materials used when the TBM is in closed excavation mode, including bentonite (an absorbent, swelling clay), which is placed into a tank and reused.
Click here for a video, here and au/38 for further information in the tunnelbuilder archive. Visit https://www.snowyhydro.com.au/. 31/23.
