Recent innovations in yield–control support systems applied to conventional tunneling in difficult ground conditions associated with squeezing are discussed in this lecture. The Saint Martin access adit along the Base Tunnel of the Lyon–Turin railway link is presented as a case study to illustrate some of the developments which have been implemented to deal with squeezing conditions encountered during excavation in the Carboniferous Formation. Also discussed are in situ performance monitoring, laboratory investigations, and advanced modeling studies performed with the aim to improve the understanding of squeezing behavior, in view of the design of the Base Tunnel.

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