ABSTRACT
High urbanization and urban migration increase demands for higher capacity transportation projects, underground. Since the mid 90’s there has been notable increase in international projects involving large diameter single bore tunnels for transit and roadway applications. The demand has been met by both TBM manufacturers, with the production of reliable TBM units pushing the diameter envelope to the range of 17-18m, and tunnel contractors ready to embark on related construction challenges. Owners and consultants have also embraced these novel approaches and supported selection and subsequent design delivery of a wide range of large diameter tunnel projects needing to meet variety of complex subsurface conditions. The paper presents benefits of large diameter tunnel application and related planning and design considerations; it includes a few examples illustrating emerging challenges, trends and innovations leading to successful implementation of this fast developing methodology.
