The TBM digging the headrace tunnel on the Australian pumped hydro project was stopped when extremely hard and abrasive rock wore down cutter discs on the edge of the cutterhead very quickly as it traversed a curve in the tunnel.
Since then, specialist contractors have been carrying out hydro blasting work to remove rock pinching on TBM Florence’s shield.
In its latest project update, Snowy Hydro says that in recent weeks “we have moved TBM Florence forward in small increments several times and the machine remains fully operational”.
The high-pressure hydro blasting breaks up and disintegrates the surrounding rock so TBM Florence can navigate the curve onto the straight headrace tunnel alignment.
At the Tantangara Reservoir, the gate shaft has been excavated and work is now focused on the two transition tunnels either side.
These tunnels are well advanced, with the full length of the top heading complete and excavation to the invert on schedule for completion in July.
The intake is now approximately 45m deep. The remaining excavation is being co-ordinated with work on the third transition tunnel.
The next stage of the intake earthworks will involve the removal of the temporary ‘rock plug’ and excavation into Tantangara Reservoir, to allow water to flow through the intake and into the headrace tunnel.
The gate shaft is one of the key structures in the overall Tantangara intake system, which also includes the intake diffuser, tunnel transitions and headrace tunnel.
The main function of the gate shaft is to stop and start the flow of water into the headrace tunnel and power station for maintenance purposes or in the case of an emergency.
