Editing Tunnel boring machine (section)

{{Short description|Device used to excavate tunnels}}
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[[File:A déli pajzs a keresztezőkamrában.jpg|thumb|One of the boring machines used for the [[Channel Tunnel]] between France and the United Kingdom]]
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A '''tunnel boring machine''' ('''TBM'''), also known as a "mole" or a "worm",{{citation needed lead|date=April 2025}} is a machine used to excavate [[tunnel]]s. TBMs are an alternative to [[drilling and blasting]] <!--(D&B) OUT until mentioned in body -->methods and "hand mining", allowing more rapid excavation through hard rock, wet or dry soil, or [[sand]] (although each requires specialized TBM technologies).{{citation needed lead|date=April 2025}} TBM-bored tunnel cross-sections extend up to {{convert|17.6|m|ft|sp=us}} (through June 2023).{{Sfn|Cecere|2023}} TBM tunnels are typically circular in cross-section, but may also be square or rectangular,{{cn|date=April 2025}} or U- or horseshoe-shaped.<ref>{{Cite news |last=Tan |first=Christopher |date=June 14, 2016 |title=New Tunnel-Boring Machine Makes Cutting Corners Perfectly Sound |newspaper=The Straits Times |url=https://www.straitstimes.com/singapore/transport/new-tunnel-boring-machine-makes-cutting-corners-perfectly-sound |url-status=live |access-date=February 27, 2020 |archive-url=https://web.archive.org/web/20200227083851/https://www.straitstimes.com/singapore/transport/new-tunnel-boring-machine-makes-cutting-corners-perfectly-sound |archive-date=February 27, 2020}}</ref><ref>{{Cite web |title="U-shape": First Shield Machine for horseshoe-shaped Cross Sections - tunnel |url=https://www.tunnel-online.info/en/artikel/tunnel_U-shape_First_Shield_Machine_for_horseshoe-shaped_Cross_Sections_2643821.html |url-status=live |archive-url=https://web.archive.org/web/20200227083854/https://www.tunnel-online.info/en/artikel/tunnel_U-shape_First_Shield_Machine_for_horseshoe-shaped_Cross_Sections_2643821.html |archive-date=2020-02-27 |access-date=2020-02-27 |website=www.tunnel-online.info}}{{full|date=April 2025}}</ref>{{full|date=April 2025}}<ref>Commercial websites that reference the same types of material include:
* {{cite web |title=Special Application TBM U-Shape TBM |url=http://www.creg-germany.com/products_tunnel-boring-machines_special-application-tbm.php |archive-url=https://web.archive.org/web/20170909235839/http://www.creg-germany.com:80/products_tunnel-boring-machines_special-application-tbm.php |archive-date=9 September 2017 |access-date=2 November 2021 |publisher=CREG Underground Solutions}}
* {{Cite web |title=Special Shield Machine &#124; Kawasaki Heavy Industries |url=https://global.kawasaki.com/en/industrial_equipment/construction/civil/special.html |url-status=live |archive-url=https://web.archive.org/web/20210926041032/https://global.kawasaki.com/en/industrial_equipment/construction/civil/special.html |archive-date=2021-09-26 |access-date=2021-10-02 |website=global.kawasaki.com}}
* {{Cite web |title=Shield Machines and Tunnel Boring Machines (TBMs) - Construction, Mining and Utility Equipment｜Products & Services｜Komatsu Ltd. |url=https://www.komatsu.jp/en/products/construction-machine/um.html |url-status=live |archive-url=https://web.archive.org/web/20230728205631/https://www.komatsu.jp/en/industries-we-support/other-industries |archive-date=2023-07-28 |access-date=2021-10-02 |website=Komatsu Ltd.}}
* {{cite web |title=Tunnel Boring Machines (Shield and TBM) |url=https://global.kawasaki.com/en/industrial_equipment/industries/Tunnel_Boring_Machines_E.pdf |url-status=live |archive-url=https://web.archive.org/web/20211001141918/https://global.kawasaki.com/en/industrial_equipment/industries/Tunnel_Boring_Machines_E.pdf |archive-date=1 October 2021 |access-date=2 November 2021 |website=global.kawasaki.com |publisher=Kawasaki}}</ref>{{better source needed|date=April 2025}} Much narrower tunnels{{what|date=April 2025}} are typically bored using [[Trenchless technology|trenchless construction]] methods or [[directional boring|horizontal directional drilling]] rather than by TBMs.{{citation needed lead|date=April 2025}} 

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TBMs limit disturbance to the surrounding ground and produce a smooth tunnel wall, which reduces the cost of lining the tunnel;{{citation needed lead|date=April 2025}} it also allows for tunneling in urban areas.{{citation needed lead|date=April 2025}} Large TBMs are expensive and challenging to construct and transport,{{citation needed lead|date=April 2025}} fixed costs which become less significant for longer tunnels.{{citation needed lead|date=April 2025}} Tunneling speeds generally decline as tunnel size increases,{{request quotation|date=April 2025}} but tunneling speeds using TBMs have nevertheless have increased over time;{{cn|date=April 2025}} the first TBM peaked at 4&nbsp;meters per week,{{when|date=April 2025}} which increased to 16&nbsp;meters per week within four decades.{{request quotation|date=April 2025}} By the end of the 19th century, speeds had reached over 30&nbsp;meters per week.{{request quotation|date=April 2025}} TBM speeds excavating through rock can, in the 21st century, reach over 700&nbsp;meters per week, while soil tunneling machines can exceed 200&nbsp;meters per week.{{Sfn|Potter|2023}}
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