Long-term performance of a machine-bored tunnel with use of an unreinforced, precast, segmented concrete lining in soft clay

A tunnel has been constructed in Thunder Bay, Canada, by use of a tunnel boring machine and an unbolted, precast, segmented concrete lining. The lining consists of 2.16-m diameter rings composed of four trapezoidal sections of unreinforced concrete 1 m in length and 11 cm thick. Each ring was assembled within the protection of the tailpiece of the tunnel boring machine. Extensive field instrumentation that provided data on performance during construction was protected after construction so that long-term monitoring could be undertaken. It is expected that observations will be continued for at least five years. The project and the performance of the tunneling system during construction are reviewed, and data from the first two years of observations following the installation of the instruments are presented. During this period a surcharge of about 1 m of soil was added over part of the tunnel alignment, including one of the two instrument arrays.Un tunnel a \ue9t\ue9 construit \ue0 Thunder Bay, au Canada, \ue0 l'aide d'une machine foreuse et d'un rev\ueatement en b\ue9ton pr\ue9fabriqu\ue9, segment\ue9 et non boulonn\ue9. Le rev\ueatement comporte des anneaux de 2.16 m de diam\ue8tre compos\ue9s de quatre sections trap\ue9zoidales en b\ue9ton non arm\ue9 (1 m de longueur et 11 cm d'\ue9paisseur). Chaque anneau a \ue9t\ue9 assembl\ue9 \ue0 l'abri du bouclier arri\ue8re de la machine foreuse. Les nombreux appareils qui ont fourni des donn\ue9es tout au long des travaux ont \ue9t\ue9 prot\ue9g\ue9s apr\ue8s la construction pour permettre une auscultation \ue0 long terme. On pr\ue9voit continuer les observations pendant au moins cinq ans. Le pr\ue9sent expos\ue9 d\ue9crit le projet et le rendement du syst\ue8me utilis\ue9 pour les travaux, puis pr\ue9sente des donn\ue9es pour les deux premi\ue8res ann\ue9es d'observation qui ont suivi la mise en place des instruments. Au cours de cette p\ue9riode, une surcharge d'environ 1 m de terre a \ue9t\ue9 ajout\ue9e sur une partie du tunnel o\uf9 se situait une des deux batteries d'instruments.Peer reviewed: YesNRC publication: Ye