Product details
Earth pressure balance
Earth pressure balance, or EPB, is a mechanised tunneling method in which the excavated material is used to support the tunnel face whilst it is being plasticised using slurry or other additives to make it transportable and impermeable. The spoil is admitted into the microtunnel boring machine (MTBM) via a screw conveyor (cochlea) arrangement which allows the pressure at the face of the MTBM 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.
EPB has historically "competed" with the slurry balance method of mechanised tunneling where the slurry is used to stabilise the tunnel face and transport spoil to the surface.
EPBMs are utilized in the construction of rail tunnels, metropolitan subway systems, highway tunnels, and other projects where the tunnel will be constructed either partly or completely in soft soil beneath the water table.
A screw conveyor removes the fluidized muck behind the cutterhead and in front of the pressure bulkhead. The screw conveyor’s speed and discharge rate is controlled by the operator and is used to control the pressure at the working face and to match the muck discharge rate to the advance rate of the EPBM.
Features of the EPB machine:
1) Applicable for all kinds of soil structure especially for coarse sand and semi-decomposed rock.
2) Low cutting speed with high cutting torque enables the drive system holding overload ratio up to 3.
3) Independent water and bentonite injection system will improve the soil stability of excavated section.
4) Low ground subsidence during construction, the earth cover depth can be reduced to 1.0 times of machine diameter.
5) Central supporting and compact design of cutter disc
6) Higher jacking force can be reached through hydro-system
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