Guide for Precast Concrete Tunnel Segments
|Publication Date:||1 April 2020|
This document provides analysis, design, and construction guidelines exclusively for one-pass precast segmental lining that is installed almost instantaneously with excavation inside TBM shields only a few yards behind the TBM cutterhead. Linings that are installed long after passing of an open-mode TBM, cast-in-place concrete linings, and segments of other materials such as steel and cast-iron segments do not fall within the scope of this guideline. Twopass lining systems, which are no longer popular in modern tunnels, are not specifically discussed but can still benefit from the guidelines. More information about the two-pass linings can be found in ITA WG2 guidelines. This guideline provides methods of design and construction for TBM tunneling in soft ground as well as weak and fractured hard rock tunneling. The guidelines and recommendations in this document can be applied to tunnels of different types, such as road, railway, and subway tunnels; headrace, water supply, and waste water tunnels; and service, gas pipeline, and power cable tunnels. The structural design part of this document pertains to procedures for designing concrete tunnel segments to withstand the commonly encountered temporary and permanent load cases occurring during the production, transportation, construction, and final service phases. The procedure was developed based on global practice and review of major available design codes, standards, and guidelines related to precast segments in tunneling and concrete industries. The construction aspects presented in this guideline including segmental ring geometry and systems, gasket systems, and connection devices, and segment tolerances reflect global practice perspectives such as ACI 544.7R, AFTES:2005, BS PAS 8810:2016, DAUB:2013, JSCE 2007, LTA 2010, ÖVBB 2011, and STUVAtec:2005. This document does not address the actions of thermal variations, fire loads and explosion, or internal loads such as train loads within the tunnels. While some structural design parts of this guideline may only consider the procedures adopted by ACI, they can be extended to other structural codes such as BS EN 1992-1-1:2004.