Tunnel segmental lining that enables rotational adjustment
The sewer outfall project Riachuelo Lote 3 (Argentina) includes a diffuser section where vertical risers are installed by applying an innovative construction method: the “Riser Concept”. The risers are jacked upward from inside the tunnel through an aperture within the tunnel segmental lining. To ensure verticality of the installed riser, precise positioning of the segmental ring that contains the aperture is required. For this purpose, the method included a system to recover the rotational misalignments of the rings caused by TBM roll. The system comprises two special segmental rings: a steel-concrete composite ring with adaptable locking system that enables the correction of the rotational misalignment (positioning ring), and a concrete ring with an embedded device that includes an aperture to allow the passage of the riser (launching ring). The special segmental rings, which have been successfully installed, were specifically designed, tested and developed to fit the purpose of vertical riser installation. The aim of this paper is to provide an overview of the most relevant aspects of the rotationally adjustable segmental lining developed, from the initial concept to the design, construction, and installation phase.