Trapezoidal Tapered Ring—Key Position Selection in Curved Tunnels
Abstract
The trapezoidal tapered ring method has made significant progress in recent years for shielded-TBM projects, excavating tunnels with high overburden, strict water tightness criteria, and multiple curve alignments. The selection of compatible tapered rings is critical for successful advancement of the tunnel, assuring efficient installation of rings, as well as prevention of ring damage and excessive leakage. Using experience from the Arrowhead Tunnels Project, this paper describes guidelines for ring selection in tunnel curves, geometric analyses that comply with criteria principals, and provides techniques developed to determine the appropriate relative key position.
2005
Samuel Swartz
Jacobs Associates
Shimi Tzobery
Hatch Mott McDonald
Gary B. Hemphill
Hatch Mott McDonald
John E. Shamma
Metro Water District of Southern California