Earth pressure balance, or EPB, is a mechanised tunneling 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.
Famous quotes containing the words earth, pressure and/or balance:
“It is the very error of the moon,
She comes more near the earth than she was wont,
And makes men mad.”
—William Shakespeare (1564–1616)
“The universal social pressure upon women to be all alike, and do all the same things, and to be content with identical restrictions, has resulted not only in terrible suffering in the lives of exceptional women, but also in the loss of unmeasured feminine values in special gifts. The Drama of the Woman of Genius has too often been a tragedy of misshapen and perverted power.”
—Anna Garlin Spencer (1851–1931)
“Forget dating. Forget striking a balance between work and family. Most single parents, whether they are divorced, widowed, or single by choice, report that discipline is by far the toughest issue.”
—Jean Callahan (20th century)