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The Bethungra Spiral is a rail spiral, built on the Main South line of New South Wales in Australia at Bethungra between Cootamundra and Junee.〔(Bethungra Spiral ) NSWrail.net〕〔(Bethungra - Frampton ) SA Track & Signal〕 The original line was graded at 1 in 40 for Sydney bound trains, which imposed a severe limitation on train loads, and also caused congestion as bank engines were attached.〔"The Bethungra Spiral Rectification Project" ''Railway Digest'' June 1994 pages 12-15〕 When the line was duplicated in the 1940s, a 8.9 kilometre spiral deviation was built. The spiral makes use of local geography in the shape of a convenient hill which the uphill line spirals around and has short tunnels. The spiral increased the distance traveled by uphill trains by about two kilometres. Downhill trains continue to use the original line. The ruling gradient of the new uphill line is was 1 in 66.〔 Due to the extensive blasting required to create 27 metre cuttings through granite, the line suffered from rockfalls with twelve significant falls between 1960 and 1987. In January 1994, the spiral line closed for a four-month rebuild which saw the cuttings widened and regraded to benched 55 degree slopes as part of the One Nation project.〔 ==References== * 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bethungra Spiral」の詳細全文を読む スポンサード リンク
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