【参考・引用元】
https://ja.wikipedia.org/wiki/宗谷本線
https://www.asahi.com/articles/ASN3Y6X36N3YIIPE00F.html
https://www.hokkaido.cci.or.jp/kousoku/
https://www.hkd.mlit.go.jp/as/douro_keikaku/vkvvn80000000or0.html
https://www.hkd.mlit.go.jp/as/release/ho928l0000005ucy-att/vktdfd000000b2nk.pdf
https://www.hkd.mlit.go.jp/ky/jg/gijyutu/slo5pa000000faek-att/slo5pa000000fd9e.pdf
https://thesis.ceri.go.jp/db/files/GR0003000120.pdf
https://thesis.ceri.go.jp/db/files/17720913705f8cf705d18e1.pdf
https://concom.jp/contents/countermeasure/column/vol12.html
https://xtech.nikkei.com/kn/article/const/news/20141211/686492/
https://www.shutoko.jp/ss/tech-shutoko/create/choukyori.html
https://www.hkd.mlit.go.jp/as/release/vktdfd0000009e3c-att/170126_otonakatunnel_2.pdf
https://www.shimz.co.jp/works/jp_tun_202206_otonaka.html
https://e-kensin.net/news/133064.html