Earth pressure balance tunnel boring machine (EPB TBM) WIRTH

Earth pressure balance tunnel boring machines
Historically, EPBs were developed in order to do away with the mucking system and the reprocessing of boring slurry. To do this, the soil must ideally consist of fine elements (clay and silt) and natural water. This type of mix is rare, which is why foams were developed.

Basic principle
The earth pressure balance tunnel boring machine or EPB consists of a cutting chamber located behind the cutterhead. This chamber is used to mix the soil + water foam. It is maintained under pressure by the mucking system. The system consists of a screw conveyor whose speed is controlled so that constant pressure inside the chamber is guaranteed. The material exits the screw conveyor via a hatch that can be closed when the TBM is shut down. The material is then removed by a belt conveyor and/or train cars circulating in the tunnel.

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