ABSTRACT
Secant piles have been traditionally used as temporary support of excavation for cut-and-cover tunnels and shafts. Alternatively, the secant piles can be integrated into the permanent structure, where it not only provides the excavation support during construction, but also forms the envelope supporting the gravity and lateral loads from the permanent structure. This offers numerous advantages, including reduced excavation cost and time for construction. This was recently used with great success in construction of an approach structure and an underground station as part of the one of the largest transit systems in North America, Réseau Express Métropolitain (REM) located in Montreal, Canada. The current paper presents a case study based on a project where secant piles were used as the permanent liner. Various structural and waterproofing solutions implemented to achieve a cost-effective design are presented along with techniques to ensure water-tight structure with more than 100 years of service life.
