Slurryshield.

The machine is used as a mixshield where gravelly geological conditions indicate an unstable tunnel face or mixed geological conditions. In this mode the extraction chamber is completely filled with suspension, while the pressure chamber (4), situated after the dive wall (1), the suspension is supported by the air pressure cushion (12) and the pressure bulkhead (2). The air pressure is automatically controlled by an air regulating equipment (10+11) to avoid blow outs and base failures at the tunnel face. The pressure compensation between the extraction chamber (3) and the suspension in the pressure chamber after the dive wall is implanted via the communicating pipe (5). The supply conduit  (9) delivers the suspension into the extraction chamber. The suspension is removed by the slurry conduit (6) from the extraction chamber behind the suction rack (13). An accumulation of sediments below the communicating pipe is avoided by an constant flush above the supply conduit (8) and the conveyor conduit (7) in the pressure chamber.

In geological conditions which indicate a stable tunnel face, e.g. in hard rock or in compacted, cohesive soils, the machine, like the smaller AVN machines, can be effectively used as a slurry shield without compressed air support. The conversion from mixshield to slurryshield takes place by sealing the conduits compressed air supply and compressed air export, the extraction chamber deairing the conveyor conduit pressure chamber, the supply conduit pressure chamber and the communicating pipe. This is also possible underground. After conversion the pressure chamber is only under atmospheric pressure because the communicating pipes have been closed. The tunnel face support is then regulated only by the suspension circuit which is pumped round the circuit by the inflow and outflow of the bentonite suspension.

For further Information, please request our brochures or our animation from our media service.

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