Design Considerations for Mega Tunnels

摘要

At approximately 60 feet (18.2 m) in diameter and about 4.5 miles long (7.2 km), the StaternRoute 710 (SR 710) Freeway Tunnel alternative, one of four multimodal alternatives under study in SouthernrnCalifornia, would be one of the largest and longest freeway tunnels in the world. Both single- and twin-borerntunnel configurations are being considered. Challenging geotechnical conditions identified along the tunnelrnalignments include mixed face conditions, high groundwater pressures, active earthquake faults, and formationsrnwith a potential for methane and hydrogen gas. This paper focuses on the design and construction challengesrnassociated with the Freeway Tunnel alternative that is being analyzed to address mobility constraints in thernstudy area.