NATM Strategies in the U.S.—Lessons Learned from the Initial Support Design for the Caldecott 4th
Abstract
The design of the Caldecott 4th Bore, located along State Route 24 in Oakland, California, is based on the principles of the New Austrian Tunneling Method (NATM). Typical NATM initial support design practices used in Europe were adapted for this project to account for U.S. conditions and requirements, such as degree of experience with NATM construction, the prevailing contractual environment, and preferences for contractual simplicity. Key design features are: (1) support selection criteria based on ground behaviors and ground conditions; (2) a prescriptive design with allowance for support adjustments based on observations during construction; and (3) organization of support requirements into only four major support categories, while permitting some adjustment for variations in ground behaviors and conditions using a few subtypes and additional support measures.
2009
Rapid Excavation and Tunneling Conference (RETC) Proceedings
Bhaskar B. Thapa
Jacobs Associates
Thomas Marcher
ILF Consultants, Austria
Michael T. McRae
Jacobs Associates
Max John
Tunnel Consultant, Austria
Zuzana Skovajsova
ILF Consultants
Mahmood Momenzadeh
California Department of Transportation
