The Lyttelton Rail Tunnel, initially called the Moorhouse Tunnel, links the city of Christchurch with the port of Lyttelton in the Canterbury region of New Zealand’s South Island. It is the country’s oldest operational rail tunnel, and is on one of the first railway lines in the district. On completion in 1867 it became the first tunnel in the world to be taken through the side of an extinct volcano, and at 2.7 km, the longest in the country. Its opening made the Ferrymead Railway, New Zealand's first public railway line, obsolete.
History
Background
Canterbury’s first settlers had two options for transporting themselves and their goods between the harbour at Lyttelton and the Canterbury plains: the Bridle Path over the Port Hills, or by ship over the Sumner Bar then up either the Heathcote or Avon Rivers.
It was therefore with concern over access to the plains that the Canterbury Provincial Council, formed in November 1853, established four months later a Commission to examine the options for improvement. Only one road route was considered feasible, the Sumner Road passing under the summit of Evans Pass via a 350-yard tunnel. There were two contenders for the rail line: a direct route down the Heathcote Valley and through a 2.5 km tunnel to the Lyttelton foreshore, or a more circuitous route via the Avon Heathcote Estuary and around the shore to Sumner, where a shorter tunnel would take the line to Gollans Bay and Lyttelton.
A tunnel is an underground or underwater passageway, dug through the surrounding soil/earth/rock and enclosed except for entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. The central portions of a rapid transit network are usually in tunnel. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.
Secret tunnels are built for military purposes, or by civilians for smuggling of weapons, contraband, or people. Special tunnels, such as wildlife crossings, are built to allow wildlife to cross human-made barriers safely.
Terminology
A tunnel is relatively long and narrow; the length is often much greater than twice the diameter, although similar shorter excavations can be constructed, such as cross passages between tunnels.