Design Guidelines for Sequential Excavation Method (SEM) Practices for Road Tunnels in the United States

Synopsis:

In the last 20 years the Sequential Excavation Method (SEM) or the New Austrian Tunneling Method (NATM) has been gaining popularity and use in the United States. Its use is versatile, in various ground conditions and at various depths. Although many of the projects were successfully completed, the lack of design guidelines for underground construction and in particular for the SEM construction, in which it relies on observational method and assessment of the ground behavior at the face, has negatively impacted the tunneling industry. Recognizing the need to develop design guidelines for underground construction, in 2007 FHWA awarded a contract to Parsons Brinckerhoff to develop and publish a design manual for road tunnels.

As a result of this contract, “Technical Manual for Design and Construction of Road Tunnels—Civil Elements” was published in November 2008. The Manual provided specific guidelines for SEM construction. This paper provides a summary of the guidelines for the design and construction of tunnels using Sequential Excavation Method with emphasis on its technical aspects, contractual issues, and practices in the US based on the recommendations and guidelines made in the above stated publication.

Design Guidelines for Sequential Excavation Method (SEM) Practices for Road Tunnels in the United States
2010 North American Tunneling Conference Proceedings
June 20-23, 2010
Portland, Oregon