NZR Tunnels: Difference between revisions
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Revision as of 08:35, 13 June 2024
INTRODUCTION
Tunnels and railways are to many people synonymous in that the early railway design philosophy in England called for near-level railways to reduce the load on the engines, but invariably led to the need for tunnels. In contrast, they then also introduced the 'inclined plane', it being the other extreme, where by railway wagons were hauled up steep grades by rope in order to reach a different 'level' of railway. These too were often through tunnels.
New Zealand being a very young country when railways were first introduced, had to tackle the issue of mountains from the very start. The options were to go round them or through them, and the engineers of the day usually took the middle ground, bu climbing up as far as practical and then piercing the ridge with a tunnel. The tunnel to Lyttelton, completed in 1863 was built very much along traditional English designs but the options of creating a shorter tunnel by climbing higher were extremely constrained due to the location of the port. Its construction proved what could be done on the other side of the world.
The Dunedin and Port Chalmers Railway (1872) was much more conservative in its approach to obstacles it could not climb over or go round. Two short tunnels met their needs but one of those has since been replaced by a much longer tunnel on a much better alignment. That is typical of much of New Zealand, the need for a tunnel will often result in a difficult track alignment up to the the tunnel making significant improvements to the alignment very expensive. North of Dunedin the mainline climbs over a significant hill with virtually continuous curves for some 15km. Along the way there were four tunnels the longest one 1.3km is currently the most restrictive tunnels on the KiwiRail network having been constructed in 1874. Several times investigations have looked at alternative routes, but even with halving the track distance and eliminating all the steep grades, it was not economic as it required a new 7 - 8km long tunnel. Similar cases would exist throughout the country with an emphasis on eliminating tunnels wherever possible due to their loading gauge constraints and challenging work environments. Recent legislation (following the Pyke River coal mine disaster) has required KiwiRail to adopt work-practices designed for mines, when working in tunnels greatly increasing the cost of all types of tunnel work.
From a peak of 130 tunnels, KiwiRail still has 100 tunnels on its network, though a significant number are on mothballed lines. The following tables give a summary of all tunnels constructed on railway lines operated by the Government railways at some point in its life. This is an interim way of presenting this dataprior to getting it all working through the Cargo database. The tables are arranged with the Line name as part of the page headings so individual Lines can be accessed more easily. They can be selected from the 'Table of Contents' at the top of the page.
Most tunnels received names, many just their location, but a good number had far more creative names, with their true origins long lost as time has gone by. There is plenty of scope to debate these origins in the discussion pages associated with each tunnels home page.
The data for the tunnel tables is currently being collated and will be added here progressively from 11/06/2024
NORTH ISLAND
North Island Main Trunk
Construction of the North Island Main Trunk line was commenced from either end long before it could be envisaged that a continuous route linking Wellington and Auckland was even possible. Because of this, non of the tunnels were built for the line they are now on. In simple terms, Wellington to Palmerston North was built by the Wellington and Manawatu Railway Company, Palmerston North to Marton was constructed as part of the line to New Plymouth Line , Marton to Ohakune was constructed for the NIMT but known as the Marton Branch until the track was linked up north of Ohakune. From the North, Auckland to Penrose was built as part of the line to Onehunga, Penrose to Te Kuiti was built as the Waikato Line and Te Kuiti to Ohakune was built for the NIMT but operated as the Auckland Section Until the line was completed. At that point in time, The line from Auckland to Wellington was operated as a complete route from Auckland, however the mileage from Auckland only ran as far as Marton, and the mileage from Wellington went all the way to New Plymouth. In 1974, when New Zealand adopted the metric system of weights and measures, all lines were remeasured and the opportunity was taken to make the NIMT a complete line in its own right with its start at Wellington (0km) and end at Auckland (681km). From that quick summary, you can see that reference to a tunnel can be quite confusing and using names will have been a convenient way of avoiding confusion. Because the km posts (the linear referencing system) start at Wellington, the data table will be presented in that order with a separate column to note the original Line name. For completeness, and as an aid to cross referencing with old documents, the original Line names will all get their own tables as well. In this way the first 12 tunnels will also be listed on the Wellington and Manawatu Railway table. Tunnel numbers in brackets indicates that tunnel is no longer used, refer to the comments column for details.
North Auckland Line
SOUTH ISLAND
Main North Line
The Main North Line was the last of the main lines to be completed and this did not happen until 1945. With the subsequent introduction of the rail ferries between Wellington and Picton, it enabled all New Zealand railways (except for the soon to close Nelson Section) to be truly called a network.
Main South Line
The Main South Line was the first line to link main centres in New Zealand by 1878 it linked Christchurch with Dunedin and Invercargill, a total distance of nearly 600km. There was also the Lyttelton Line linking Christchurch with its port at Lyttelton and this was incorporated in the Main South Line very early on. The line passes through extremely varied county with long stretches of very easy going, to a number of very difficult sections, particularly around Dunedin. A total of 11 tunnels were required, one to access the port at lyttelyon, the longest tunnel in the British empire at the time, one just south of Oamaru, and the other 9 all close to Dunedin. Three of those were replaced by double track tunnels early in the 20th century, one was bypassed due to unstable ground, and one short one was daylighted rather than enlarged to accommodate shipping containers. The remaining four all had extensive work carried out to enable container traffic to pass on standard wagons. Mihiwaka tunnel, the longest of those was constructed in 1874 and is now the narrowest tunnel still in use by KiwiRail. The following table lists all the Main South Line tunnels with their important details.