Tunneling employing a sequential excavation philosophy represents a unique intersection between planning, design and construction. It depends on the behavior of the ground and the construction methods, size of the opening and support measures, and the rate of advancement. It allows adaptation to changing conditions, for which the team must work collaboratively and flexibly, applying the observational method to share and manage project risk.

Over the last five decades there has been a rapid advancement in computational capabilities, understanding of ground pressures and...