ACI 533.5R-20

The worldwide trend in construction is toward mechanization and automation. This trend has led to continued rapid progress of mechanized tunneling. Advantages over conventional tunnel construction methods include, but are not limited to, occupational health and safety, faster advance rates, and reducing construction labor requirements. Mechanized tunneling in soft ground using tunnel boring machines is often associated with installing precast concrete segmental lining. However, very little industry-wide guidance has been provided by practice and code organizations. This document provides guidelines for precast concrete tunnel segments, including the most recent developments and practical experience, in addition to information on all aspects of design and construction. These guidelines are based on the knowledge and the experience gained on numerous precast tunnel projects in the United States, and available national and international guidelines often used as industry references.