ABSTRACT
Due to increasing traffic volume, the need for additional ventilation or escape routes, as well as the repair and reinforcement of aging tunnels, it is necessary to research tunnel enlargement methods. This study compiles 12 tunnel enlargement cases from around the world to summarize tunnel enlargement technology, planning, and design, including survey items, enlargement direction, traffic considerations, lining structure types, enlargement methods, support design, and blasting vibration influence. Finally, an actual case of planning and design for the enlargement of a road tunnel in South America is used as the basis for explaining the planning and design concepts used for the enlargement of an existing tunnel. Numerical analysis was used to verify the stability and safety of tunnel enlargement supports at each stage, with the goal of creating a reference for future tunnel enlargement planning and design.
