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  • Gripper TBM

    Boring Dia. 8.1 m,
    YinSong Water Divison

  • Metro EPB Tel Aviv

    Boring Dia. 7.54

  • EPB & Rectangular

Earth Pressure Balance

Earth pressure balance, or EPB, is a mechanized tunneling method in which the excavated material is used to support the tunnel face whilst it is being plasticised using foam/slurry & other additives to make it transportable and impermeable. The excavated material is transported into the tunnel boring machine (TBM) via a screw conveyor arrangement which allows the pressure at the face of the TBM to remain balanced without the use of slurry.

EPB Tunnel Boring Machines are mainly designed for soft soils containing water under pressure. The EPB TBM can handle loose sedimentary deposits with large boulders and high water table.

The excavated material is transported by a screw conveyor from the excavation chamber to the belt conveyor. The combination of the output of the screw conveyor and the advance rate of the TBM ensures that the support pressure in the excavation chamber can be exactly controlled. Continuously monitoring of the state of balance in the excavation chamber by means of earth pressure sensors, allows the operator to control and synchronize all tunneling parameters. It allows high advance rates and reduces the risk of changes at the surface.

To improve the ground conditions for EPB tunnelling several conditioning materials can be injected through the cutter head and the bulk head. By changing the ground conditions tunnelling in soils containing gravel, sand or water or in unstable geology is also possible

The cutter head of the machine will be designed specially for the ground conditions of the project. Depending on the requirements the head will be equipped with disc cutters or rippers, or a combination of both. All cutter heads will have an optimized opening ratio.


The CREG EPB TBMs have an articulated shield. The articulated joint between front and tail shield is equipped with seals allowing angular movement between the shields and prevents the ingress of water.

The screw conveyor removes the muck from the excavation chamber.

For difficult geology with big pebbles the TBM can be equipped with ribbon type screw conveyor instead of standard screw conveyor.

Metro Shenzhen, China

CREG supplied twenty-seven TBM´s to Shenzhen Metro Project. Geology therein is mainly featured by slightly weathered granite and boulders. In the TBM design cutter spacing is reduced, cutterhead drive torque increased and cutterhead/-main bearing capacity enhanced to withstand uneven load. All CREG TBM´s are highly geologically adaptable in Shenzhen Metro. TBM CREC-68 achieved maximum daily advance rate 24m and monthly 558m.
Geology Museum of Geology
  • Granite (80-160MPa)
  • Mixed faceClay, Sand, Gravel
Excavation Dia. 6980 mm
Drive Power 1120 kW (Electric/VFD)
Advance rates In Granite GIV-GVI: Average 15 m/day ; In GII/GIII: Average 7,5 m/day
Cutterhead design feature
  • Smaller Cutter Spacing: 75mm
  • Opening: Evenly distributed
Performance Max advance 28.5m/day, 559.5m/month

Metro Kuala Lumpur, Malaysia

Malaysia’s capital Kuala Lumpur is constantly increasing its Mass Rapid Transit underground network. Two Tunnel Boring Machines supplied by CREG have excavated two tunnels with a boring diameter of 6,67m in water saturated sandy mudstone, schistose mudstone, highly weathered mudstone as well as alluvium with a maximum advance rate of more than 345m/month.
Project Data
Project nameKlang Valley MRT
Total tunnel lengthApprox. 2,2 km
PurposeMetro
Ground conditionsLimestone, sandstone, mudstone
Challenges
  • Max. monthly advance rate: 347,2 m
  • Settlement max < 3 mm
TBM Data
TBM TypeEPB
Boring diameter6,63 m
Cutter head power1120 kW
Max. torque7000 kNm
Total weight750 t
Max. working pressure5 bar

Metro Chengdu, China

The capital of Sichuan is the very quick growing city Chengdu. To quickly establish an underground metro system CREG has supplied 32 Tunnel Boring Machines, which were designed to cope with the ground conditions that consist mostly of mudstone and water rich sandy gravel.
Project Data
Project nameChengdu Metro
Total tunnel length> 50 km
PurposeMetro
Ground conditionsWater saturated gravels, boulders
Challenges
  • Max. daily advance rate: 31,5 m
  • Max. monthly advance rate: 607,5 m
  • 852 m of advance without cutter tools replacement
TBM Data
TBM TypeEPB
Boring diameter6,28 m
Cutter head power945 kW (hydraulic)
Max. torque8100 kNm
Total weight800 t
Max. working pressure3 bar

Metro Tel Aviv, Israel

To extend the Tel Aviv metro system CREG supplies in total six sets of EPB Tunnel Boring machines for metro extension. The Red line will extend for 24 kilometres, 11 of which will be underground and excavated by Tunnel Boring Machines.
Project Data
Project nameRed Line Project
Total tunnel length11 km
PurposeMetro
Ground conditionsArgillaceous sand, Kurkar ground
Challenges
  • Quartz content in ground is up to 60%
  • Cutting wheel is designed to withstand high wear
TBM Data
TBM TypeEPB
Boring diameter7,54 m
Cutter head power1600 kW
Max. torque12000 kNm
Total weight850 t
Max. working pressure7 bar