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:
“Laugh, and the world laughs with you;
Weep, and you weep alone,
For the sad old earth must borrow its mirth,
But has trouble enough of its own.”
—Ella Wheeler Wilcox (1850–1919)
“Amid the pressure of great events, a general principle gives no help.”
—Georg Wilhelm Friedrich Hegel (1770–1831)
“Mental health depends upon the maintenance of a balance within the personality between the basic human urges and egocentric wishes on the one hand and the demands of conscience and society on the other hand.”
—Selma H. Fraiberg (20th century)