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Tunnel boring machines (
TBM) excavate tunnels with a circular cross section through a variety of
geology. They can be used to bore through hard rock or sand and almost anything in between. Tunnel diameters can range from a metre (done with micro-TBMs) to 15 metres. The two biggest were built in 2005 to dig two tunnels for the same urban project in
Madrid (Spain). Dulcinea and Tizona, as they were called, have diameters of 15 metres.
Tunnels of less than a metre or so in diameter are more typically done by directional boring rather than by TBMs.
Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods. A TBM has the advantages of not disturbing surrounding soil and producing a smooth tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in built-up areas. The key disadvantage is cost. TBMs are expensive to construct, difficult to transport and require significant infrastructure.
Description
A tunnel boring machine (TBM) typically consists of one or two shields (large metal cylinders) and trailing support mechanisms.At the front end of the shield a rotating cutting wheel is located. Behind the cutting wheel there is a chamber where, depending on the type of the TBM, the excavated soil is either mixed with slurry (so-called
slurry TBM) or left as-is. The choice for a certain type of TBM depends on the soil conditions. Systems for removal of the soil (or the soil mixed with slurry) are also present.Behind the chamber there is a set of hydraulic jacks supported by the finished part of the tunnel which push the TBM forward. The action here is very much like an earthworm. The rear section of the TBM is braced against the tunnel walls and used to push the TBM head forward. At maximum extension the TBM head is then braced against the tunnel walls and the TBM rear is dragged forward.Behind the shield, inside the finished part of the tunnel, several support mechanisms which are part of the TBM can be found: dirt removal, slurry
Pipeline transports if applicable, control rooms, rails for transport of the precast segments, etc. The cutting wheel will typically rotate at 1 to 10 rpm (depending on size and geology), cutting the rock face into chips or excavating soil (muck). Depending on the type of TBM, the muck will fall onto a conveyor belt system and be carried out of the tunnel, or be mixed with slurry and pumped back to the tunnel entrance. Depending on geology and tunnel requirements, the tunnel may be cased, lined, or left unlined. This may be done by bringing in precast concrete sections that are jacked into place as the TBM moves forward, by assembling concrete forms, or in some hard rock geologies, leaving the tunnel unlined and relying on the surrounding rock to handle and distribute the load.
Image:Tunnelier mp3h8085.jpgImage:Tunnelier mp3h8086.jpg
Shields
Modern TBMs typically have an integrated Tunneling shield. The choice of a single or double shielded TBM depends on the type of geology and the excavation speed required.
Double shielded TBMs are normally used in unstable geology, or where a high rate of advancement is required. Single shielded TBMs, which are less expensive, are more suitable to hard rock geology.
Urban tunneling and near surface tunneling
Urban tunneling has the special challenge of requiring that the ground surface be undisturbed. This means that ground subsidence must be avoided. The normal method of doing this is to maintain the soil pressures during and after the tunnel construction.
There is some difficulty in doing this, particularly in varied geologies (imagine tunnel boring through a region where the upper portion of the tunnel face is wet sand and the lower portion is hard rock).
TBMs with positive face control are used in such situations. There are three common types: Earth pressure balance (EPB),
Bentonite slurry (BS), and compressed air (CA). The compressed air method is the oldest, but is falling out of favour due to the difficult working conditions it imposes.
Both types (EPB and BS) are clearly preferred over open face methods in urban environments as they offer far superior ground control.
When tunneling in urban environments other tunnels and deep foundations need to be addressed in the early planning stages. The project must accommodate measures to mitigate any detrimental effects to other infrastructure.
History
In 1853, one of the first boring machines built was used during the construction of the
Hoosac Tunnel. Constructed out of cast iron, it was known as Wilson's Patented Stone-Cutting Machine, after its inventor Charles Wilson. It managed to drill 10 feet into the rock before breaking down.
See also
References
External links
- 2.M-30 EPB Tunnel Boring Machine-the largest built in the world
.
Tunnel boring machines (
TBM) excavate
tunnels with a circular cross section through a variety of
geology. They can be used to bore through hard rock or
sand and almost anything in between. Tunnel diameters can range from a metre (done with micro-TBMs) to 15 metres. The two biggest were built in 2005 to dig two tunnels for the same urban project in Madrid (Spain). Dulcinea and
Tizona, as they were called, have diameters of 15 metres.
Tunnels of less than a metre or so in diameter are more typically done by directional boring rather than by TBMs.
Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods. A TBM has the advantages of not disturbing surrounding soil and producing a smooth tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in built-up areas. The key disadvantage is cost. TBMs are expensive to construct, difficult to transport and require significant infrastructure.
Description
A tunnel boring machine (TBM) typically consists of one or two shields (large metal cylinders) and trailing support mechanisms.At the front end of the shield a rotating cutting wheel is located. Behind the cutting wheel there is a chamber where, depending on the type of the TBM, the excavated soil is either mixed with
slurry (so-called
slurry TBM) or left as-is. The choice for a certain type of TBM depends on the soil conditions. Systems for removal of the soil (or the soil mixed with slurry) are also present.Behind the chamber there is a set of
hydraulic jacks supported by the finished part of the tunnel which push the TBM forward. The action here is very much like an
earthworm. The rear section of the TBM is braced against the tunnel walls and used to push the TBM head forward. At maximum extension the TBM head is then braced against the tunnel walls and the TBM rear is dragged forward.Behind the shield, inside the finished part of the tunnel, several support mechanisms which are part of the TBM can be found: dirt removal, slurry Pipeline transports if applicable, control rooms, rails for transport of the precast segments, etc. The cutting wheel will typically rotate at 1 to 10
rpm (depending on size and geology), cutting the rock face into chips or excavating soil (muck). Depending on the type of TBM, the muck will fall onto a conveyor belt system and be carried out of the tunnel, or be mixed with slurry and pumped back to the tunnel entrance. Depending on geology and tunnel requirements, the tunnel may be cased, lined, or left unlined. This may be done by bringing in
precast concrete sections that are jacked into place as the TBM moves forward, by assembling concrete forms, or in some hard rock geologies, leaving the tunnel unlined and relying on the surrounding rock to handle and distribute the load.
Image:Tunnelier mp3h8085.jpgImage:Tunnelier mp3h8086.jpg
Shields
Modern TBMs typically have an integrated Tunneling shield. The choice of a single or double shielded TBM depends on the type of geology and the excavation speed required.
Double shielded TBMs are normally used in unstable geology, or where a high rate of advancement is required. Single shielded TBMs, which are less expensive, are more suitable to hard rock geology.
Urban tunneling and near surface tunneling
Urban tunneling has the special challenge of requiring that the ground surface be undisturbed. This means that ground subsidence must be avoided. The normal method of doing this is to maintain the soil pressures during and after the tunnel construction.
There is some difficulty in doing this, particularly in varied geologies (imagine tunnel boring through a region where the upper portion of the tunnel face is wet sand and the lower portion is hard rock).
TBMs with positive face control are used in such situations. There are three common types:
Earth pressure balance (EPB), Bentonite slurry (BS), and compressed air (CA). The compressed air method is the oldest, but is falling out of favour due to the difficult working conditions it imposes.
Both types (EPB and BS) are clearly preferred over open face methods in urban environments as they offer far superior ground control.
When tunneling in urban environments other tunnels and deep foundations need to be addressed in the early planning stages. The project must accommodate measures to mitigate any detrimental effects to other infrastructure.
History
In 1853, one of the first boring machines built was used during the construction of the Hoosac Tunnel. Constructed out of cast iron, it was known as Wilson's Patented Stone-Cutting Machine, after its inventor Charles Wilson. It managed to drill 10 feet into the rock before breaking down.
See also
- Boring (mechanical)
- Channel Tunnel
- New Austrian Tunnelling method
- SMART Tunnel
- Tunnel
- Tunneling
- Tunneling shield
References
External links
- 2.M-30 EPB Tunnel Boring Machine-the largest built in the world
Tunnel boring machine - Wikipedia, the free encyclopedia
A tunnel boring machine (TBM) is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand ...
Tunnel boring machine - What does TBM stand for? Acronyms and ...
Acronym Definition; TBM: Tunnel Boring Machine: TBM: The Birthday Massacre (band) TBM: Theater Ballistic Missile: TBM: Three Blind Mice: TBM: Tactical Ballistic Missile
Tunnel boring machine - Wikimedia Commons
Deutsch: Eine Tunnelbohrmaschine (TBM) ist eine Maschine, welche zum Bau von Tunneln eingesetzt wird.
Morgan Est :. Early Solutions Together - News
A 13-tonne tunnel boring machine, has been successfully lowered into a shaft in Aughton, near Ormskirk, by leading infrastructure services provider Morgan Est.
Morgan Est :. Early Solutions Together - News
Tunnelling specialist Morgan Est has successfully lowered a tunnel boring machine into a shaft in Ross-on-Wye as work progresses on a major flood alleviation scheme in the town.
YouTube - tbm Tunnel boring Machine
Rate: 43 ratings. Sign in to rate. Views: 43,475. Share: Favorite: Playlists: Flag: MySpace. Facebook. Digg (more share options) (fewer share options) This video will appear on ...
News
News. Breakthrough! – February 2008. Breaking into daylight again after 15 months of tunnelling through the heart of the mountain, the massive TBM (Tunnel Boring Machine) arrived ...
BUILDING BIG: Glossary
Tunnel Boring Machine (TBM)-a mechanical device that tunnels through the ground. Tunnel Shield-a cylinder pushed ahead of tunneling equipment to provide advance support for the ...
Tunnel Boring Machine
Tunnel boring machine. ... The website for the road traffic industry
Tunnel Boring Machine
Combined Sewer Overflow (CSO) Sneak a peek at the NBC's tunnel boring machine! Still in construction in Japan, the tunnel boring machine (TBM) is ...
