ASCE will be sunsetting the Civil Engineering Database (CEDB) in the coming months. We encourage you to start using the ASCE Library to perform content searches. In the ASCE Library, you can save your search results as well as receive email content alerts when new content relevant to your area of interest is published. Try it out today at https://ascelibrary.org.

 

Unearthing Mt. Baker Tunnel

by Edgar B. Johnson, (F.ASCE), Partner in Charge; HNTB, Seattle, WA,
Lee J. Holloway, (M.ASCE), Chf. Structural Engrg.; HNTB, Seattle, WA,
Georg Kjerbol, (M.ASCE), Senior Project Engineer; HNTB, Seattle, WA,


Serial Information: Civil Engineering—ASCE, 1985, Vol. 55, Issue 12, Pg. 36-39


Document Type: Feature article

Abstract:

A new tunnel under Mt. Baker in Seattle is part of major improvements to I-90 between Bellevue and Seattle's business district. Feasibility studies began in 1963, but it was not until 1977 that the concept of a single bored tunnel was accepted by WSDOT. Conventional full face tunneling was not suitable for the site, which had silty clays beneath a residential area. Instead, the stacked drift liner system was used, with 24 bores driven in a circular pattern and filled with concrete before excavation began on the 63 ft diameter tunnel. The liner was designed as a semi-flexible support system capable of adjusting to non-uniform external loading by deforming until equilibrium is reached. Structurally, it acts as a ring in compression. Because they are only 9 ft in diameter, the drifts were excavated with conventional equipment. Access pits 90 ft in diameter and 90 ft deep were converted to vertical retaining walls for the cut-and-cover end portions of the 1,500 ft tunnel.

Subject Headings: Tunnels | Linings | Feasibility studies | Excavation | Clays | Tunneling | Silt

Services: Buy this book/Buy this article

 

Return to search