Design of NATM Initial Support on the Caldecott 4th Bore
Abstract
The proposed Caldecott 4th Bore, located along State Route 24 in Oakland, California is a 15 m wide, 9.7 m high, highway tunnel that will be constructed using the New Austrian Tunneling Method (NATM). Rock mass strength and deformability properties including local effects due to strain softening, intact rock softening and strength degradation due to erosion and softening of joint infillings are key design considerations for the project. Ground/structure interaction issues modeled in numerical analyses include stress relaxation ahead of the tunnel heading, arching of loads across weak zones, face stability, effects of early age creep in shotcrete and stress redistributions due to the formation of plastic hinges in the shotcrete lining. The design also evaluated forces, moments and rotations in the shotcrete lining to determine ground support requirements.
2008
American Rock Mechanics Association (ARMA) Conference Proceedings
Jason Choi
Jacobs Associates
Bhaskar B. Thapa
Jacobs Associates
Michael T. McRae
Jacobs Associates
