Micro Tunnelling
Our Slurry Machines with a cone crusher are all-rounders for safe tunnelling in the diameter
range of 0.4 to around 4 meters. These micro tunnelling experts show their full potential
particularly in non-accessible machine sizes. The slurry-supported excavation concept
makes it possible to use these machines in all kinds of ground conditions, ranging from
silt to clay to incohesive soils, and further to gravel and rock. Depending on the diameter,
this is possible both in pipe jacking and for segmental lining.
The Machines belong to the category of closed, full face excavation machines with a
hydraulic slurry circuit. The soil to be excavated is removed using a cutterhead adapted
to the respective geology. This makes it possible to use the machines in almost all geological
conditions. In soft soils and mixed geologies, standard or mixed ground cutterheads are used,
while a rock cutterhead with disc cutters is used for tunnelling in stable rock formations.
A cone-shaped crusher inside the excavation chamber crumbles stones and other obstructions
to a conveyable grain size while tunnelling and advancing. Afterwards, the material falls
through openings like a strainer in front of the suction port and is then removed through
the slurry line together with the suspension. The excavation diameter can be enlarged
using an upsize kit and a modified cutterhead. This means that the AVN Machine can be
used to tunnel different diameters and for different types of pipes.
AVND Machines are equipped with an additional pressure chamber behind the excavation
chamber. AVN technology has been expanded to offer extra safety in non-homogeneous,
less stable geological conditions and for larger diameters. Like Mixshields, the support
pressure is controlled using a communicating pipe and an automatically controlled air
cushion inside the pressure chamber. This allows for even more precise control at a
heterogeneous tunnel face and reduces the pressure peaks in the excavation chamber.
This makes AVND Machines specialists for tunnelling operations sensitive to settlement
even under high groundwater pressure and with shallow overburdens.