Tunnel boring machine

Short description: Device used to excavate tunnels

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One of the boring machines used for the Channel Tunnel between France and the United Kingdom

A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. TBMs are an alternative to drilling and blasting 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} up to 17.6 meters (58 ft) (through June 2023).[1] TBM tunnels are typically circular in cross-section, but may also be square or rectangular or U- or horseshoe-shaped.[2][3][full citation needed][4] Much narrower tunnels are typically bored using trenchless construction methods or horizontal directional drilling rather than by TBMs.

TBMs limit disturbance to the surrounding ground and produce a smooth tunnel wall, which reduces the cost of lining the tunnel and allows for tunneling in urban areas. Large TBMs are expensive and challenging to construct and transport, fixed costs which become less significant for longer tunnels.{{citation needed lead|date=April 2025} tunnel size increases,[need quotation to verify] but tunneling speeds using TBMs have nevertheless increased over time.[citation needed] TBM speeds excavating through rock can, in the 21st century, reach over 700 meters per week, while soil tunneling machines can exceed 200 meters per week.[5]

## Contents

* 1 History
* 1.1 1800s
* 1.2 1900s
* 1.3 2000s
* 2 Types
* 2.1 Tunnel wall types
* 2.1.1 Concrete lining
* 2.1.2 Main beam
* 2.2 Shield types
* 2.2.1 Open/gripper
* 2.2.2 Single shield
* 2.2.3 Double shield
* 2.3 Tunnel-face support methods
* 2.3.1 Earth pressure balance
* 2.3.2 Slurry shield
* 2.3.3 Open face soft ground
* 2.4 Tunnel size
* 3 Backup systems
* 4 Urban tunnelling and near-surface tunnelling
* 5 See also
* 6 Notes
* 7 References
* 8 Further reading
* 9 External links

## History

Cutting shield used for the New Elbe Tunnel Looking towards the cutting shield at the hydraulic jacks A tunnel boring machine cutter head being lowered underground for the construction of the City & Southwest line of the Sydney Metro

### 1800s

The first successful tunnelling shield was developed by Sir Marc Isambard Brunel to excavate the Thames Tunnel in 1825. However, this was only the invention of the shield concept and did not involve the construction of a complete tunnel boring machine, the digging still having to be accomplished by the then standard excavation methods.[6]

The first boring machine reported to have been built was Henri Maus' Mountain Slicer.[7][8] [9][10] Commissioned by the King of Sardinia in 1845 to dig the Fréjus Rail Tunnel between France and Italy through the Alps, Maus had it built in 1846 in an arms factory near Turin. It consisted of more than 100 percussion drills mounted in the front of a locomotive-sized machine, mechanically power-driven from the entrance of the tunnel. The Revolutions of 1848 affected the funding, and the tunnel was not completed until 10 years later, by using less innovative and less expensive methods such as pneumatic drills.[11]

In the United States, the first boring machine to have been built was used in 1853 during the construction of the Hoosac Tunnel in northwest Massachusetts.[12] Made of cast iron, it was known as Wilson's Patented Stone-Cutting Machine, after inventor Charles Wilson.[13] It drilled 3 meters (10 ft) into the rock before breaking down (the tunnel was eventually completed more than 20 years later, and as with the Fréjus Rail Tunnel, by using less ambitious methods).[14] Wilson's machine anticipated modern TBMs in the sense that it employed cutting discs, like those of a disc harrow, which were attached to the rotating head of the machine.[15][16][17] In contrast to traditional chiseling or drilling and blasting, this innovative method of removing rock relied on simple metal wheels to apply a transient high pressure that fractured the rock.[citation needed]

In 1853, the American Ebenezer Talbot also patented a TBM that employed Wilson's cutting discs, although they were mounted on rotating arms, which in turn were mounted on a rotating plate.[18] In the 1870s, John D. Brunton of England built a machine employing cutting discs that were mounted eccentrically on rotating plates, which in turn were mounted eccentrically on a rotating plate, so that the cutting discs would travel over almost all of the rock face that was to be removed.[19][20]

The first TBM that tunneled a substantial distance was invented in 1863 and improved in 1875 by British Army officer Major Frederick Edward Blackett Beaumont (1833–1895); Beaumont's machine was further improved in 1880 by British Army officer Major Thomas English (1843–1935).[21][22][23][24][25] In 1875, the French National Assembly approved the construction of a tunnel under the English Channel and the British Parliament supported a trial run using English's TBM. Its cutting head consisted of a conical drill bit behind which were a pair of opposing arms on which were mounted cutting discs. From June 1882 to March 1883, the machine tunneled, through chalk, a total of 1,840 m (6,036 ft).[10] A French engineer, Alexandre Lavalley, who was also a Suez Canal contractor, used a similar machine to drill 1,669 m (5,476 ft) from Sangatte on the French side.[26] However, despite this success, the cross-Channel tunnel project was abandoned in 1883 after the British military raised fears that the tunnel might be used as an invasion route.[10][27] Nevertheless, in 1883, this TBM was used to bore a railway ventilation tunnel — 2 m (7 ft) in diameter and 2.06 km (6,750 ft) long — between Birkenhead and Liverpool, England, through sandstone under the Mersey River.[28]

Construction of the Uptown Hudson Tubes for the Hudson & Manhattan Railroad took place intermittently between 1890 and 1908, using a Greathead Shield. The project used air compressed to 2.4 bar (35 psi) to reduce cave-ins. However, there were many workers that died via cave-in or decompression sickness.[29][30][5]

### 1900s

During the late 19th and early 20th century, inventors continued to design, build, and test TBMs for tunnels for railroads, subways, sewers, water supplies, etc. TBMs employing rotating arrays of drills or hammers were patented.[31] TBMs that resembled giant hole saws were proposed.[32] Other TBMs consisted of a rotating drum with metal tines on its outer surface,[33] or a rotating circular plate covered with teeth,[34] or revolving belts covered with metal teeth.[35] However, these TBMs proved expensive, cumbersome, and unable to excavate hard rock; interest in TBMs therefore declined. Nevertheless, TBM development continued in potash and coal mines, where the rock was softer.[36]

A TBM with a bore diameter of 14.4 m (47 ft 3 in) was manufactured by The Robbins Company for Canada's Niagara Tunnel Project. The machine was used to bore a hydroelectric tunnel beneath Niagara Falls. The machine was named "Big Becky" in reference to the Sir Adam Beck hydroelectric dams to which it tunnelled to provide an additional hydroelectric tunnel.

### 2000s

A tunnel boring machine used to excavate the Gotthard Base Tunnel, Switzerland, the world's longest rail tunnel

The TBM known as Bertha, reportedly the largest earth pressure balance machine and second largest TBM in general (as of June 2023), has a bore diameter of 17.45 meters (57.3 ft), and was produced by Hitachi Zosen Corporation in 2013.[1][37] It was delivered to Seattle, Washington, for its Highway 99 tunnel project.[38][full citation needed] The machine began operating in July 2013, but stalled in December 2013 and required substantial repairs that halted the machine until January 2016.[39] Bertha completed boring the tunnel on April 4, 2017.[40][full citation needed]

Two TBMs supplied after the 2013 acquisition of Germany's Aker Wirth (Aker Solutions) TBM and shaft-boring technology by China Railway Tunnelling Equipment (CRTE), now CREG (China Railway Engineering Equipment Group)-Germany,[41][42] CREG-Wirth units with boring diameter of 6.67 m (21.9 ft), were used to bore two tunnels for Kuala Lumpur, Malaysia's Metro system.[42]{{better source|date=April 2025} "saturated sandy mudstone, schistose mudstone, highly weathered mudstone as well as alluvium".[42][better source needed] By the company's commercial de an advance rate of "more than 345 meters [1,130 feet] per month".[42][better source needed]

Top view of a model of the TBM[clarification needed] used on the Gotthard Base Tunnel.[citation needed]

Reportedly the largest hard rock machine and fourth largest TBM overall (as of June 2023), a machine known as Martina, was built by Herrenknecht AG.[1] Its excavation diameter is 15.62 m (51.2 ft), and total length 130 m (430 ft); excavation area of 192 m2 (2,070 sq ft), and thrust value 39,485 t,[clarification needed] total weight 4,500 tons, and total installed capacity 18 MW.[1] Its yearly energy consumption was about 62 GWh.[1] Martina was used by the Italian Toto Group construction company (Toto S.p.A Costruczioni General) to bore a 2.4 km tunnel of the Variante di Valico project near Florence, Italy, in 2013. This project created the Sparvo gallery of the Italian Motorway Pass A1 ("Variante di Valico A1"), near Florence.[citation needed] As of this date,[when?] Martina was still owned and operated by the Toto Group.[citation needed]

Herrenknecht also built the world's largest-diameter slurry TBM and as of June 2023, per Guinness World Records, also the largest TBM overall; called the "Qin Liangyu" or Mixshield S-880, it has an excavation diameter of 17.63 meters (57.8 ft).[1] Owned and operated by a subsidiary of the French construction company Bouygues (Dragages Hong Kong), it was used to bore the Chek Lap Kok to Tuen Mun road tunnel, undersea, to Hong Kong, China, clearing the first section of the tunnel at the large diameter, then being converted to 14 m, and working alongside 3 other TBMs (including another Herrenknect borer) to complete the tunnels, 30 m undersea, in 2019.[1]

##  Types

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A tunnel boring machine that was used at Yucca Mountain nuclear waste repository

TBMs typically consist of a rotating cutting wheel in front, called a cutter head, followed by a main bearing, a thrust system, a system to remove excavated material (muck), and support mechanisms. Machines vary with site geology, amount of ground water present, and other factors.

Rock boring machines differ from earth boring machines in the way they cut the tunnel, the way they provide traction to support the boring activity, and in the way they support the newly formed tunnels walls.

### Tunnel wall types

#### Concrete lining

Hydraulic jacks holding a TBM in place

Shielded TBMs are typically used to excavate tunnels in soil. They erect concrete segments behind the TBM to support the tunnel walls.[43] The machine stabilizes itself in the tunnel with hydraulic cylinders that press against the shield, allowing the TBM to apply pressure at the tunnel face.

#### Main beam

Main beam machines do not install concrete segments behind the cutter head. Instead, the rock is held up using ground support methods such as ring beams, rock bolts, shotcrete, steel straps, ring steel and wire mesh.[43]

### Shield types

Depending on the stability of the local geology, the newly formed walls of the tunnel often need to be supported immediately after being dug to avoid collapse, before any permanent support or lining has been constructed. Many TBMs are equipped with one or more cylindrical shields following behind the cutter head to support the walls until permanent tunnel support is constructed further along the machine. The stability of the walls also influences the method by which the TBM anchors itself in place so that it can apply force to the cutting head. This in turn determines whether the machine can bore and advance simultaneously, or whether these are done in alternating modes.

#### Open/gripper

Gripper TBMs are used in rock tunnels. They forgo the use of a shield and instead push directly against the unreinforced sides of the tunnel.[5]

Machines such as a Wirth machine can be moved only while ungripped. Other machines can move continuously. At the end of a Wirth boring cycle, legs drop to the ground, the grippers are retracted, and the machine advances. The grippers then reengage and the rear legs lift for the next cycle.

#### Single shield

A single-shield TBM has a single cylindrical shield after the cutting head. A permanent concrete lining is constructed immediately after the shield, and the TBM pushes off the lining to apply force to the cutter head. Because this pushing cannot be done while a next ring of lining is being constructed, the single-shield TBM operates in alternating cutting and lining modes.

#### Double shield

Double shield (or telescopic shield) TBMs have a leading shield that advances with the cutting head and a trailing shield that acts as a gripper. The two shields can move axially relative to each other (i.e., telescopically) over a limited distance. The gripper shield anchors the TBM so that pressure can be applied to the cutter head while simultaneously the concrete lining is being constructed.

### Tunnel-face support methods

In hard rock with minimal ground water, the area around the cutter head of a TBM can be unpressurized, as the exposed rock face can support itself. In weaker soil, or when there is significant ground water, pressure must be applied to the face of the tunnel to prevent collapse and/or the infiltration of ground water into the machine.

#### Earth pressure balance

Tunnel boring machine at the site of Weinberg tunnell Altstetten-Zürich-Oerlikon near Zürich Oerlikon railway station Urban installation for an 2.1-meter (84 in) sewer in Chicago, IL, USA The support structures at the rear of a TBM. This machine was used to excavate the main tunnel of the Yucca Mountain nuclear waste repository in Nevada.

Earth pressure balance (EPB) machines are used in soft ground with less than 7 bar (100 psi) of pressure. It uses muck to maintain pressure at the tunnel face. The muck (or spoil) is admitted into the TBM via a screw conveyor. By adjusting the rate of extraction of muck and the advance rate of the TBM, the pressure at the face of the TBM can be controlled without the use of slurry. Additives such as bentonite, polymers and foam can be injected ahead of the face to stabilize the ground. Such additives can separately be injected in the cutter head and extraction screw to ensure that the muck is sufficiently cohesive to maintain pressure and restrict water flow.

Like some other TBM types, EPB's use thrust cylinders to advance by pushing against concrete segments. The cutter head uses a combination of tungsten carbide cutting bits, carbide disc cutters, drag picks and/or hard rock disc cutters.

EPB has allowed soft, wet, or unstable ground to be tunneled with a speed and safety not previously possible. The Channel Tunnel, the Thames Water Ring Main, sections of the London Underground, and most new metro tunnels completed in the last 20 years worldwide were excavated using this method. EPB has historically competed with the slurry shield method (see below), where the slurry is used to stabilize the tunnel face and transport spoil to the surface. EPB TBMs are mostly used in finer ground (such as clay) while slurry TBMs are mostly used for coarser ground (such as gravel).[44]

#### Slurry shield

Slurry shield machines can be used in soft ground with high water pressure or where granular ground conditions (sands and gravels) do not allow a plug to form in the screw. The cutter head is filled with pressurised slurry, typically made of bentonite clay that applies hydrostatic pressure to the face. The slurry mixes with the muck before it is pumped to a slurry separation plant, usually outside the tunnel.

Slurry separation plants use multi-stage filtration systems that separate spoil from slurry to allow reuse. The degree to which slurry can be 'cleaned' depends on the relative particle sizes of the muck. Slurry TBMs are not suitable for silts and clays as the particle sizes of the spoil are less than that of the bentonite. In this case, water is removed from the slurry leaving a clay cake, which may be polluted.

A caisson system is sometimes placed at the cutting head to allow workers to operate the machine,[45][46] although air pressure may reach elevated levels in the caisson, requiring workers to be medically cleared as "fit to dive" and able to operate pressure locks.[45][46]

#### Open face soft ground

Open face soft ground TBMs rely on the excavated ground to briefly stand without support. They are suitable for use in ground with a strength of up to about 10 MPa (1,500 psi) with low water inflows. They can bore tunnels with cross-section in excess of 10 m (30 ft). A backactor arm or cutter head bore to within 150 mm (6 in) of the edge of the shield. After a boring cycle, the shield is jacked forward to begin a new cycle. Ground support is provided by precast concrete, or occasionally spheroidal graphite iron (SGI) segments that are bolted or supported until a support ring has been added. The final segment, called the key, is wedge-shaped, and expands the ring until it is tight against the ground.

### Tunnel size

TBMs range diameter from 1 to 17 meters (3 to 56 ft). Micro tunnel shield TBMs are used to construct small tunnels, and is a smaller equivalent to a general tunnelling shield and generally bore tunnels of 1 to 1.5 meters (3.3 to 4.9 ft), too small for operators to walk in.

## Backup systems

Behind all types of tunnel boring machines, in the finished part of the tunnel, are trailing support decks known as the backup system, whose mechanisms can include conveyors or other systems for muck removal; slurry pipelines (if applicable); control rooms; electrical, dust-removal and ventilation systems; and mechanisms for transport of pre-cast segments.

## Urban tunnelling and near-surface tunnelling

Urban tunnelling has the special requirement that the surface remain undisturbed, and that ground subsidence be avoided. The normal method of doing this in soft ground is to maintain soil pressures during and after construction.

## See also

* Engineering:New Austrian tunneling method - Method of modern tunnel design and construction
* Engineering:Roadheader
* Engineering:Subterrene
* Engineering:Trenchless technology - Underground construction that minimizes surface disruption

## Notes

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Cecere 2023. sfn error: no target: CITEREFCecere2023 (help)
2. ↑ Tan, Christopher (June 14, 2016). "New Tunnel-Boring Machine Makes Cutting Corners Perfectly Sound". The Straits Times. https://www.straitstimes.com/singapore/transport/new-tunnel-boring-machine-makes-cutting-corners-perfectly-sound.
3. ↑ ""U-shape": First Shield Machine for horseshoe-shaped Cross Sections - tunnel". https://www.tunnel-online.info/en/artikel/tunnel_U-shape_First_Shield_Machine_for_horseshoe-shaped_Cross_Sections_2643821.html. [full citation needed]
4. ↑ Commercial websites that reference the same types of material include:
* "Special Application TBM U-Shape TBM". CREG Underground Solutions. http://www.creg-germany.com/products_tunnel-boring-machines_special-application-tbm.php.
* "Special Shield Machine | Kawasaki Heavy Industries". https://global.kawasaki.com/en/industrial_equipment/construction/civil/special.html.
* "Shield Machines and Tunnel Boring Machines (TBMs) - Construction, Mining and Utility Equipment｜Products & Services｜Komatsu Ltd.". https://www.komatsu.jp/en/products/construction-machine/um.html.
* "Tunnel Boring Machines (Shield and TBM)". Kawasaki. https://global.kawasaki.com/en/industrial_equipment/industries/Tunnel_Boring_Machines_E.pdf.
5. ↑ 5.0 5.1 5.2 Potter 2023.
6. ↑ Bagust 2006, p. 65.
7. ↑ Drinker 1883, pp. 191-194.
8. ↑ West 1988.
9. ↑ Maidl et al. 2008.
10. ↑ 10.0 10.1 10.2 Hemphill 2013.
11. ↑ Hapgood, Fred, "The Underground Cutting Edge: The innovators who made digging tunnels high-tech",Invention & Technology Vol.20, #2, Fall 2004
12. ↑ Maidl et al. 2008, p. 1.
13. ↑ Smith, Gary. "Finding Aid for the Hoosac Tunnel Collection at the North Adams Public Library". Hooac Tunnel Historical Notes. North Adams Public Library. http://www.naplibrary.com/HTHistoricNotes.html.
14. ↑ Howes, M. "Hoosac Tunnel History - Abridged Timeline". http://www.hoosactunnel.net/historytimeline.php.
15. ↑ Bancroft 1908, p. 65
16. ↑ Wilson, Charles. "Dressing stone," U.S. Patent 5,012 (issued: March 13, 1847).
17. ↑ Wilson, Charles. "Machine for tunneling rocks, etc.," U.S. Patent 14,483 (issued: March 18, 1856).
18. ↑ Talbot, Ebenezer. "Machine for tunnelling or boring rock," U.S. Patent 9,774 (issued: June 7, 1853).
19. ↑ West 1988, pp. 239–242.
20. ↑ Brunton, John D. "Improved machine for sinking shafts," U.S. Patent 80,056 (issued: July 21, 1868).
21. ↑ West 1988, pp. 243–247.
22. ↑ David William Brunton and John Allen Davis, Modern Tunneling: With Special Reference to Mine and Water-supply Tunnels (New York, New York: John Wiley & Sons, 1914), p. 182.
23. ↑ Frederick Edward Blackett Beaumont, U.K. Patent no. 1,904 (issued: July 30, 1864). (See: Patents for Inventions. Abridgments of Specifications relating to Mining, Quarrying, Tunnelling, and Well-sinking (London, England: Office of the Commissioners of Patents for Inventions, 1874), p. 247. )
24. ↑ F.E.B. Beaumont, U.K. Patent no. 4,166 (issued: Dec. 2, 1875). (See: Patents for Inventions. Abridgments of Specifications. Class 85, Mining, Quarrying, Tunnelling, and Well-sinking (London, England: Patent Office, 1904), p. 169. )
25. ↑ Thomas English, U.K. Patent no.s 4,347 (issued: October 25, 1880) and 5,317 (issued: December 5, 1881); "Tunneling-machine," U.S. Patent 307,278 (filed: June 4, 1884 ; issued: October 28, 1884).
26. ↑ Wilson, Jeremy; Spick, Jérôme (1994). Eurotunnel: The Illustrated Journey. New York, NY, USA: Harper Collins. pp. 14–21. ISBN 0-00-255539-5.
27. ↑ Terry Gourvish, The Official History of Britain and the Channel Tunnel (Abington, England: Routledge, 2006), Chapter 1, § 2: The commercial possibilities: Lord Richard Grosvenor, Sir Edward Watkin and the 'Manchester to Paris Railroad'.
28. ↑ West 1988, p. 248.
29. ↑ "Hudson and Manhattan Railroad Tunnel". Reston, VA: American Society of Civil Engineers (ASCE). https://www.asce.org/about-civil-engineering/history-and-heritage/historic-landmarks/hudson-and-manhattan-railroad-tunnel.
30. ↑ "Hudson & Manhattan Tunnel". New York, NY: ASCE Metropolitan Section. https://www.ascemetsection.org/committees/history-and-heritage/landmarks/hudson-manhattan-tunnel.
31. ↑ See:
* Bancroft 1908, pp. 66, 125, 127, 146.
* Thales Lindsey, "Improved machine for tunneling rock," U.S. Patent 55,514 (issued: June 12, 1866).
* Pedro Unanue, "Tunneling machine," U.S. Patent 732,326 (filed: December 23, 1901; issued: June 30, 1903).
* Russell B. Sigafoos, "Rotary tunneling machine," U.S. Patent 901,392 (filed: May 18, 1907; issued: October 20, 1908).
* George A. Fowler, "Tunnel driving machine," U.S. Patent 891,473 (filed: July 30, 1907 ; issued: June 23, 1908).
32. ↑ See:
* Bancroft 1908, pp. 66, 85, 106.
* Wilson, Charles. Machine for excavating tunnels," U.S. Patent 17,650 (issued: June 23, 1857).
* Stanley, Reginald. U.K. Patent no. 1,449 (issued: February 1, 1886); "Tunneling-machine" (issued: August 7, 1894).
* Mitchell, Jonas L. "Tunneling-machine," U.S. Patent 537,899 (filed: April 3, 1893 ; issued: April 23, 1895).
33. ↑ See:
* William F. Cooke and George Hunter, U.K. patent no. 433 (issued: August 10, 1866). Available online at: AditNow .
* Patents for Inventions. bridgments of Specifications relating to Mining, Quarrying, Tunnelling, and Well-sinking (London, England: Office of the Commissioners of Patents for Inventions, 1874), p. 275.
* Maidl et al. 2008
34. ↑ See:
* Bancroft 1908, pp. 146, 165.
* John P. Karns, "Tunneling-machine," U.S. Patent 848,107 (filed: November 29, 1905; issued: March 26, 1907).
* Olin S. Proctor, "Tunneling-machine," U.S. Patent 900,951 (filed: February 17, 1908; issued: October 13, 1908).
35. ↑ See:
* Bancroft 1908, p. 145.
* William A. Lathrop, "Machine for cutting headings," U.S. Patent 816,923 (filed: August 31, 1903; issued: April 3, 1906).
36. ↑ For example:
* In Germany, the Eisener Bergmann (iron miner) was developed in 1916 by Schmidt, Kranz & Co. for potash mines; its boring head consisted of a large rotating roller that was fitted with cutters See: Maidl et al. 2008
* In the U.S., the McKinlay Entry Driver, a track-mounted TBM or "continuous miner", was invented in 1918 for use in coal mines. Its boring head consisted of metal tines on two, side-by-side rotating arms. See: Thomas W. Garges (November 13, 2003) William N. Poundstone lecture: "Underground Mining Technology Evolution", p. 8. Available online at: Benjamin M. Statler College of Engineering and Mineral Resources, West Virginia University
37. ↑ "Shield Tunneling Machines" (in en). https://www.hitachizosen.co.jp/english/business/field/infrastructure/shield.html. [full citation needed][third-party source needed]
38. ↑ "Alaskan Way Viaduct - Home". http://www.wsdot.wa.gov/projects/Viaduct/. [full citation needed]
39. ↑ Weise, Karen (2016-01-06). "Bertha the Giant Drill Is Ready to Rumble in Seattle". Bloomberg Businessweek (Bloomberg.com). https://www.bloomberg.com/news/articles/2016-01-06/bertha-the-giant-drill-is-ready-to-rumble-in-seattle/. Retrieved 21 July 2017.
40. ↑ "Alaskan Way Viaduct - Recapping Bertha's breakthrough". 2017-04-06. https://www.wsdot.wa.gov/Projects/Viaduct/library/advisories-and-updates/recapping-berthas-breakthrough. [full citation needed]
41. ↑ IM Staff (29 November 2013). "Aker Sells TBM and Shaft Sinking Businesses to China's CRTE". International Mining (IM, IM-Mining.com). Berkhamsted, England: IM Team Publishing. https://im-mining.com/2013/11/29/aker-seels-underground-development-business-to-chinas-crte/. Note, the acquisition was sans Wirth's newer Mobile Tunnel Miner technology developed with Codelco and Rio Tinto, see article.
42. ↑ 42.0 42.1 42.2 42.3 CREG-Wirth Staff (2017-09-09). "Earth Pressure Balance" (manufacturer's commercial site). CREG-Germany.com. Erkelenz, Germany: CREG TBM Germany GmbH. Metro Kuala Lumpur, Malaysia > Project; and Metro Kuala Lumpur, Malaysia > Tech Specs. http://www.creg-germany.com/products_tunnel-boring-machines_epb-machine.php#tab-c-03. [third-party source needed]
43. ↑ 43.0 43.1 Stack 1995.
44. ↑ Shen, Si (25 October 2021). "TBM selection - EPB and SlurrySi Shen". https://www.si-eng.org/post/tbm-selection.
45. ↑ 45.0 45.1 Walters, D. "Sydney Airport Link Rail Tunnel Project, Des Walters: Under Pressure Underground". Descend Underwater Training Centre.. http://www.descend.com.au/commercial/projects/2003413191.htm.
46. ↑ 46.0 46.1 Bennett, MH; Lehm, J; Barr, P. "Medical support for the Sydney Airport Link Tunnel project". South Pacific Underwater Medicine Society 32 (2). http://archive.rubicon-foundation.org/7673. Retrieved 2008-10-08.

## References

* Bagust, Harold (2006). The Greater Genius?: A Biography of Marc Isambard Brunel. Shepperton, England: Ian Allan Publishing. ISBN 0711031754. https://books.google.com/books?vid=ISBN0711031754. Retrieved 22 April 2025.
* Bancroft, George J. (July 23, 1908). "A History of the Tunnel Boring Machine: A Series of Articles on the Various Forms and Patents under which the Tunnel Boring Machine has Appeared Since 1856". Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (4): 65–68. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA65. Retrieved 22 April 2025.

* Bancroft, George J. (July 30, 1908). "A History of the Tunnel Boring Machine: The Second of a Series of Articles on the Various Forms and Patents under which the Tunnel Boring Machine has Appeared Since 1856". Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (5): 85–88. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA85. Retrieved 22 April 2025.
* Bancroft, George J. (August 6, 1908). "A History of the Tunnel Boring Machine: The Second [sic. of a Series of Articles on the Various Forms and Patents..."]. Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (6): 106ff. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA106. Retrieved 22 April 2025.
* Bancroft, George J. (August 13, 1908). "A History of the Tunnel Boring Machine: The Fourth of a Series of Articles on the Various Forms and Patents...". Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (7): 125ff. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA125. Retrieved 22 April 2025.
* Bancroft, George J. (August 20, 1908). "A History of the Tunnel Boring Machine: The Fifth of a Series of Articles on the Various Forms and Patents...". Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (8): 145f. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA145. Retrieved 22 April 2025.
* Bancroft, George J. (August 27, 1908). "A History of the Tunnel Boring Machine: The Sixth of a Series of Articles on the Various Forms and Patents...". Mining Science (Denver, CO: The Mining Science Publishing Co.) 58 (9): 165f. https://books.google.com/books?id=m-RAAQAAMAAJ&pg=PA165. Retrieved 22 April 2025.

* Cathy, Cecere (June 13, 2023). "5 Biggest Tunnel Boring Machines in the World". New York, NY: American Society of Mechanical Engineers (ASME). https://www.asme.org/topics-resources/content/5-biggest-tunnel-boring-machines-in-the-world.
* Drinker, Henry Sturgis. Treatise on Explosive Compounds, Machine Rock Drills and Blasting (New York, New York: J. Wiley & Sons, 1883), pp. 191-194.
* Hemphill, Gary B. Practical Tunnel Construction (Hoboken, New Jersey: John Wiley & Sons, 2013), Chapter 7: Tunnel-boring machines: History of tunnel-boring machine.
* Maidl, Bernhard; Schmid, Leonhard; Ritz, Willy; Herrenknecht, Martin (2008). Hardrock Tunnel Boring Machines. Ernst & Sohn. ISBN 978-3-433-01676-3.
* Potter, Brian (6 October 2023). "The Evolution of Tunnel Boring Machines" (in en). Construction-Physics.com. https://www.construction-physics.com/p/the-evolution-of-tunnel-boring-machines.
* Stack, Barbara (1995) Encyclopaedia of Tunnelling, Mining, and Drilling Equipmen.[full citation needed]
* West, Graham (1988) "Ch. 11: Hard Rock Tunnelling Machines", in Innovation and the Rise of the Tunnelling Industry, Cambridge, England: Cambridge University Press, pages 239-248.

## Further reading

* Barton, Nick (2000). TBM tunnelling in jointed and faulted rock. Rotterdam: Balkema.
* Bilger, Burkhard (September 15, 2008). "The Long Dig: Getting through the Swiss Alps the hard way". The New Yorker.
* Foley, Amanda (May 2009). "Life on the Cutting Edge: Dick Robbins". Tunnels & Tunnelling International.

## External links

| Wikimedia Commons has media related to:

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* Robbins. "Tunneling World Records" (in en-US). https://www.robbinstbm.com/news-and-media/world-records/.

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