Rimutaka Tunnel

Infobox tunnel
name = Rimutaka Tunnel


caption =
line = Wairarapa Line
location = Rimutaka Ranges, Wellington, New Zealand
coordinates =
system = ONTRACK
status = Open
start = Maymorn, Upper Hutt
end = Rimutaka Loop
stations =
open = 3 November 1955
close =
owner = ONTRACK
operator = Toll Rail, Tranz Metro
character = passenger/freight
linelength = 8.798km
tracklength =
notrack = single
gauge = 1067mm
el = provided for 1500vDC but not installed
speed = 100km/h
hielevation =
lowelevation=
height =
grade =|The Rimutaka Tunnel is a railway tunnel through New Zealand's Rimutaka Ranges, between Maymorn, near Upper Hutt, and Featherston, on the Wairarapa Line.

Length

The tunnel is 8.798 kilometres (5.467 miles) long, the second-longest tunnel in New Zealand, and allegedly the Southern Hemisphere. It was the longest tunnel in New Zealand, superseding the Otira Tunnel in the South Island, but in 1978 the Kaimai Tunnel (8.88 km, 5.55 miles) near Tauranga opened. It is now the longest tunnel in New Zealand with scheduled passenger trains.

History

The tunnel was built as part of a deviation to replace the costly Rimutaka Incline and its Fell engines, and the first shot was fired in 1948. The deviation opened on 3 November 1955, five days after the incline closed.

Design and construction

The deviation's ruling grade is 1 in 70, compensated for curvature. The tunnel rises at 1 in 400 from the western portal to the highest point on the deviation, roughly halfway through the tunnel, and then descends to the eastern portal at 1 in 180. [Keller, 1954; p. 404] It has an internal height of 5.18 metres (17 ft) and a width of 4.68 metres (15 feet 4 inches); it is lined with concrete with a minimum thickness of 38 cm (15 inches) inside the face of the excavation. When the tunnel holed through on 20 April 1954 the surveying error was found to be only 44.5 mm (1.75 inches). [Keller, 1954; p. 413]

After its completion, a 2.74 metre (9 ft) diameter vertical ventilation shaft was driven up from a point almost halfway through the tunnel. It reaches the surface beside the Rimutaka Rail Trail near the former route's Pakuratahi Tunnel. The 117 metre (380 ft) high shaft was constructed after tests showed that the tunnel would not generate enough natural ventilation without it. The original specification using electric locomotives did not require the level of ventilation that was required to clear the tunnel of exhaust fumes generated by the subsequently used diesel traction.

The construction of the Rimutaka Tunnel consumed::*Gelignite: 299,258 kg (659,750 lbs),:*Detonators: 327,850,:*Diesel fuel: 3,182,264 litres (700,000 imp. gallons),:*Cement: 26,163 tonnes (25,750 tons),:*Aggregate: 87,837 metres³ (114,886 cu. yd), and:*Timber: 15,820 metres³ (6,703,533 super feet). [Keller, 1954; p. 416]

Traction

Diesel-Electric

The first locomotives to work through the tunnel were the 792 kW DG class - the tunnel was too long for steam locomotives, making the Wairarapa Line the first fully dieselised line in New Zealand. Today, DBR, DC and DX class locomotives run the route.

team

The annual Daffodil Carnival steam train from Wellington to Carterton has to be hauled by diesel-electrics attached to the front of the steam locomotive between Upper Hutt and Featherston, through the tunnel.

Electric

There have been proposals to electrify the tunnel and the Wairarapa line as far north as Masterton as an extension of the Wellington suburban electrification. The tunnel was designed to enable catenary to be installed but this has not happened, and the catenary finishes just north of Upper Hutt station.

Use of the tunnel

Passenger

Tranz Metro operates passenger services named the Wairarapa Connection between Wellington and Masterton via the tunnel five times a day each way Monday to Thursday, six on Friday, and twice a day each way on Saturday, Sunday, and public holidays. Excursion trains also go through the tunnel, such as railway enthusiast specials and trains to the Toast Martinborough festival. Steam-hauled excursions require diesel locomotives to provide motive power through the tunnel due to the dangers of smoke in the tunnel's lengthy and confined conditions.

Freight

The tunnel is used by some Wellington to Napier freight trains, and for freight from the Wairarapa to Wellington, notably wood products from the Juken Nissho timber mill at Waingawa, just south of Masterton.

Notes

References

* Anon. (1950) " [http://www.ukrailarchive.org/nz/rm08-1950-543.PDF The Rimutaka Incline and Deviation, New Zealand] ", "Railway Magazine", 96 (592: August), p. 543–547
* Keller, G. P. (1954) "The Rimutaka Deviation", "New Zealand Engineering", 9 (12: 15 December), p. 399–420