CATSBY: Collapse real-time prevention system for slurry tunnel boring machines in soft ground

For slurry shield tunnel boring machines in soft soils, the Bouygues' Signal Aided Boring concept (CATSBY system, for Creusement Assiste par Traitement du Signal - Bou Ygues) has demonstrated its ability not only to automatically detect microcollapses at the tunnel face (alarm signals) but also to anticipate the emergence of favourable conditions to their occurrence (risk level variation indicators), This paper describes the basic principles on which Signal Aided Boring is based, and the experiments carried out on two tunnels to develop this concept.