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Tunnel boring machines (TBM) are used to excavate tunnels with a circular cross section through a variety of geologies. 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. Tunnel boring machine at the construction of Yucca Mountain. ...
Tunnel boring machine at the construction of Yucca Mountain. ...
Yucca Mountain Yucca Mountain is a ridge-line in Nye County, Nevada; composed of volcanic material (mostly tuff) ejected from a now-extinct caldera-forming supervolcano. ...
A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ...
The Blue Marble: The famous photo of the Earth taken en route to the Moon by Apollo 17s Harrison Schmitt on December 7, 1972. ...
Patterns in the sand Sand is an example of a class of materials called granular matter. ...
Madrid is the capital and the largest city in Spain, as well as in the province and the autonomous community of the same name. ...
Tunnels of less than a metre or so in diameter are more typically done by horizontal directional drilling rather than by TBMs. Straightline 2020 Horizontal Directional Drill Horizontal Directional Drilling (HDD) is a trenchless construction technique, which uses guided drilling for creating an arc profile. ...
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. Before the advent of tunnel boring machines, drilling and blasting was the only economical way of excavating long tunnels through hard rock, where digging is not possible. ...
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. A slurry is a mixture, which comes in different varieties: Metal Slurry can be used in pipe fitting and other welding tasks, as well as slurry based bombs like the BLU-82. ...
 Hydraulic jacks holding a TBM in place. Behind the chamber there is a set of hydraulic jacks supported by the finished part of the tunnel which are used to push the TBM forward. The action here is caterpillar-like. 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. Image File history File linksMetadata Download high resolution version (1704x2272, 1946 KB) Summary Taken by R.A.Rainton 15 Feb 2005. ...
Image File history File linksMetadata Download high resolution version (1704x2272, 1946 KB) Summary Taken by R.A.Rainton 15 Feb 2005. ...
Hydraulics is a branch of science and engineering concerned with the use of liquids to perform mechanical tasks. ...
The striking caterpillar of the Emperor Gum Moth This article is about insect larva. ...
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 pipelines if applicable, control rooms, rails for transport of the precast segments, etc.
The cutting wheel will typically rotate at 4 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. rpm or RPM may mean: revolutions per minute RPM Package Manager (originally called Red Hat Package Manager) RPM (movie) RPM (band), a Brazilian rock band RPM (magazine), a former Canadian music industry magazine In firearms, Rounds Per Minute: how many shots an automatic weapon can fire in one minute On...
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. Precast concrete is an ancient type of construction material made with concrete cast in a reusable mold or form and cured in a controlled environment, then transported to the construction site and lifted into place. ...
Shields Modern TBMs typically have an integrated shield. The choice of a single or double shielded TBM depends on the type of geology and the excavation speed required. Image File history File links Download high resolution version (819x614, 221 KB) Schneiderad der Schildvortriebsmaschine Tief Runter Unter Die Elbe für den 2. ...
Image File history File links Download high resolution version (819x614, 221 KB) Schneiderad der Schildvortriebsmaschine Tief Runter Unter Die Elbe für den 2. ...
New Elbe Tunnel The tunnel with its length of 2. ...
A tunnelling shield is a protective structure used in the excavation of tunnels through soil that is too soft or fluid to remain stable during the time it takes to line the tunnel with a support structure of concrete or steel. ...
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. Earth pressure balance (EPB) EPB refers to a mechanised tunnelling method in which spoil is admitted into the tunnel boring machine (TBM) via a screw arrangement which allows the pressure at the face of the TBM to remain balanced without the use of slurry. ...
Bentonite - USGS Bentonite is an absorbent aluminium phyllosilicate generally impure clay consisting mostly of montmorillonite, (Na,Ca)0. ...
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.
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