Earth pressure balance
Encyclopedia
Earth pressure balance, or EPB, is a mechanised tunnel
ing method in which spoil
is admitted into the tunnel boring machine
(TBM) via a screw conveyor
(cochlea) arrangement which allows the pressure at the face of the TBM to remain balanced without the use of slurry
.
This 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 world wide were excavated using this method.
EPB has historically "competed" with the slurry wall
method of mechanised tunneling where the slurry is used to stabilise the tunnel face and transport spoil to the surface.
Tunnel
A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
ing method in which spoil
Spoil (archaeology)
In Archaeology, spoil is the term used for the soil, dirt and rubble that results from an excavation, and discarded off site on spoil heaps. These heaps are commonly accessed by barrow runs.-Spoil management:...
is admitted into the tunnel boring machine
Tunnel boring machine
A tunnel boring machine also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through anything from hard rock to sand. Tunnel diameters can range from a metre to almost 16 metres to date...
(TBM) via a screw conveyor
Screw conveyor
A screw conveyor or auger conveyor is a mechanism that uses a rotating helical screw blade, called a "flighting", usually within a tube, to move liquid or granular materials. They are used in many bulk handling industries...
(cochlea) arrangement which allows the pressure at the face of the TBM to remain balanced without the use of slurry
Slurry
A slurry is, in general, a thick suspension of solids in a liquid.-Examples of slurries:Examples of slurries include:* Lahars* A mixture of water and cement to form concrete* A mixture of water, gelling agent, and oxidizers used as an explosive...
.
This has allowed soft, wet, or unstable ground to be tunneled with a speed and safety not previously possible.
The Channel Tunnel
Channel Tunnel
The Channel Tunnel is a undersea rail tunnel linking Folkestone, Kent in the United Kingdom with Coquelles, Pas-de-Calais near Calais in northern France beneath the English Channel at the Strait of Dover. At its lowest point, it is deep...
, the Thames Water Ring Main
Thames Water Ring Main
The Thames Water Ring Main is a major part of London's water supply infrastructure that consists of an approximately 80 km system of mostly concrete pipelines used to transfer potable water from water treatment works in the Thames and River Lee catchments to distribution within London.The...
, sections of the London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...
, and most new metro
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...
tunnels completed in the last 20 years world wide were excavated using this method.
EPB has historically "competed" with the slurry wall
Slurry wall
A slurry wall is a technique used to build reinforced-concrete walls in areas of soft earth close to open water or with a high ground water table. This technique is typically used to build diaphragm walls surrounding tunnels and open cuts, and to lay foundations.A trench is excavated to create a...
method of mechanised tunneling where the slurry is used to stabilise the tunnel face and transport spoil to the surface.
See also
- Tunnel boring machineTunnel boring machineA tunnel boring machine also known as a "mole", is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through anything from hard rock to sand. Tunnel diameters can range from a metre to almost 16 metres to date...
- TunnelTunnelA tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
s - BoringBoring (earth)Boring is drilling a hole, tunnel, or well in the earth.-Earth boring:Boring is used for a wide variety of applications in geology, agriculture, hydrology, civil engineering, and oil and natural gas industries...