This month we’ll update you on tunnel boring machine (TBM) Kirsten, which is putting Snowy 2.0 at the forefront of TBM tunnelling innovation, along with the unique concrete segments she will install as part of the inclined pressure shaft excavation and lining.
Damon Miller, Senior Engineering & Quality Manager for Snowy 2.0, works with the design, manufacturing and construction teams to plan and deliver the engineering solutions behind Snowy 2.0, the pumped hydro expansion of the Snowy Scheme.
Building the inclined pressure shaft (IPS) will be a unique and technically challenging engineering feat for the project team
After finishing the 2.9 kilometre Emergency Cable and Ventilation Tunnel, TBM Kirsten has been substantially modified for her next critical role excavating the IPS.
This very steep, 1.6 kilometre, 10 metre diameter shaft forms part of the waterway and will connect the headrace tunnel with the underground power station.
Project director Dave Evans believes the specially manufactured segments being used for this shaft are going to change the world of hydropower. “It means we can do less steel lining, we can move power stations closer to the surface which is what we’ve done here and construct an inclined pressure shaft with a tunnel boring machine which all makes it safer, quicker and the quality a lot better.”
To see the latest Snowy 2.0 project statistics, view the fact sheet here.
To cope with the extreme and fluctuating water pressures in the IPS, the concrete segment rings lining the tunnel require bespoke connectors.
The Force Activated Coupling System or FACS are specially-developed steel couplers with pin and socket elements.
When the segment rings are interlocked, the pre-stressed FACS keep the joint closed when the tunnel experiences sharp changes in pressure from turbine operations and shut downs. It’s like water hammer when opening or closing a tap at home, just on a much larger scale.
This new technology has been developed by Future Generation joint venture partner Webuild and their designer Lombardi, with the FACS segments being manufactured at our precast factory in Cooma.
A large-scale test is being conducted by installing eight FACS rings to link the emergency, cable and ventilation tunnel with the IPS.
Meanwhile, innovative design by the leading TBM manufacturer Herrenknecht has allowed TBM Kirsten to be modified to safely tunnel uphill.
The machine’s working platforms, equipment and operator’s cabins all pivot to remain horizontal and the walkways become steps and ladderways.
A screw conveyor will move excavated rock from the cutterhead. This feeds into a sandwich conveyor that has face-to-face rubber belts to hold the material so it can be transported down the steep slope without spillage.
The IPS is on a 47% incline so a monorail is being installed to transport workers and there is a rack and pinion system for multi-service vehicle access including segment delivery up the steep slope to the TBM.