Tunneling update – Road header commissioning and trial

Two Sandvik MT 520 road headers, each weighing around 115 tonnes, will be our prime construction equipment for the two diversion tunnels, which will play a crucial part in diverting the river to construct the dam.

To ensure a smooth kick off for tunnel operations, which will commence in mid-August, the road headers were commissioned in early June and field trials were carried out on June 21 and 22. The trial was aimed at replicating the environment inside the tunnel by setting up a tent close to the rock surface and carrying out the excavation of rock.

The front part of the road header, with the cutting head and water-spraying system, breaks the rock while the attached conveyor transports the broken rocks to a truck positioned nearby. A dust extraction (suction) fan – with the ducts extending up to the face of the rock – was installed to meet with the standards of dust level in the operating zone. This was the sequence of operation experimented in the trial.

The road header trial provided us with some valuable insights into the dust extraction system and the cutting effectiveness on the rock we will be dealing with for a length of around 1,500 metres (including both diversion tunnels). The road headers will start operating by mid August and will work through the tunnels for a period of ten months.