Construction of second underwater tunnel for the hydropower plant Manapouri NZ. The Manapouri plant is the largest electric energy producer of New Zealand. With its ex-tension the capacity was raised from 565 to a total of 760 megawatt. The second underwater tunnel is located in a natural preserve park of NZ. Environmental factors were carefully considered in the design of the overall planning.
From the very beginning special circumstances concerning ground con-ditions, rock hardness potential rock burst, faults, and areas with fragile rock conditions had to be factored in. High ground water inflow was expected.
According to the demanding heading works Rowa developed a logistics system of the newest generation at the time. It included installations for rock support with steel beams, rock bolts, nets, and shotcrete, and the supply and removal of the heading.
The back-up is consisting of two main units, back-up car 1 with rock support and infrastructure areas and back-up car 2 with suspended platforms and supply and removal installations. Back-up car 1, supported on walking legs, stands still during heading and advances with the resetting of the TBM grippers. The back-up is being pulled by the TBM and glides during advancing on the walking legs which allow steering through sideway movements. The walking legs are capable to walk over steel ring beams and rock bolts.
Rowa developed a special vibrating channel with finger screen that is able to separate the muck in terms of size. Oversize rocks bigger than 250mm are being hindered from reaching the back-up conveyor and are guided to the invert to be crushed to smaller pieces. An elevator transports this material upwards and throws it on the back-up conveyor.