Toadmoor Tunnel (originally called Hag Wood Tunnel) was built at Ambergate as part of the North Midland Railway, which opened in 1840. 128 yards long, it was cut through an unstable hillside on a notoriously difficult line of route. What had initially been expected to be acceptably strong coal-bearing rock turned out to be wet shale. On beginning excavation a landslide occurred, the effects of which can still be seen further up the bank in Thatcher's Wood.Alan Baxter and Associates in ''World Heritage News,'' Issue 14, 2014, Derwent Valley Mills Partnership The engineer

Frederick Swanwick Frederick Swanwick (1810–1885) was an English civil engineer who assisted George Stephenson, George and Robert Stephenson. He was responsible for much of the work on railways in the North and Midlands of England, particularly the Whitby and P ...

decided to proceed using the cut-and- cover method, with stone retaining walls and invert, and a brick-built masonry arch over the top, which gives it its unusual elliptical shape. Because of this, it took 15 months to build, instead of the planned two. It is thought that a second landslip may have occurred sometime later, so that it was braced with steel hoops at its southern end. Because of the tunnel cross section the depth of ballast under the track is adequate in the centre but almost nothing close to the walls, which produces settlement in the middle and crushed ballast at the edges.Balfour Beatty: Polyurethane slab track 4 August 2014
/ref> Other problems arise with a need for increased line speed and the arrival of electrification, not least because it is

grade 2 listed In the United Kingdom, a listed building or listed structure is one that has been placed on one of the four statutory lists maintained by Historic England in England, Historic Environment Scotland in Scotland, in Wales, and the Northern Irel ...

and part of the Derwent Valley

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...

External links

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"Picture the Past" Toadmoor Tunnel c.1957

References

{{coord, 53.06051, N, 1.48070, W, region:GB_source:enwiki-osgb36(SK349516), display=title Rail transport in Derbyshire Railway tunnels in England History of Derbyshire Tunnels in Derbyshire Tunnels completed in 1839