Herrenknecht AVN are all-rounders for safe tunnelling in the diameter range of 0.4 to around 4 meters. The slurry-supported excavation concept makes it possible to use these machines in all kinds of ground conditions. The slurry-supported excavation concept makes it possible to use these machines in all kinds of ground conditions, ranging from slit to clay to incohesive soils, and further to gravel and rock.