Role of Engineering Geology on Rehabilitation of Likelike Highway Wilson Tunnel
Abstract
One of the major highway crossings of the Koolau Mountains between Honolulu and the windward coast of Oahu, the Wilson Tunnel is comprised of one-half mile long twin tunnels, each carrying 2-lanes of traffic. Leakage into the tunnel has been persistent since construction. The recent rehabilitation consisted of remediating tunnel lining cracks and leakage, as well as improve wall finishes.
During construction of the first tunnel in 1954, full-face excavation transitioned from competent volcanic rock to extremely weathered rock and soil, which ultimately led to sinkholes and tunnel collapses that killed five construction workers. This incident is one of the more famous tunnel failure case histories, and was investigated by notable figures such as Karl Terzaghi, Ralph Peck and Donovan Jacobs. Tunnel construction was successfully completed between 1956 and 1960 using the "stacked drift" tunneling method.
Tunnel inspection and evaluation efforts began in 2002. The tunnel inspection, combined with as-built and historical information on construction and engineering geology, was the basis for evaluations of alternative rehabilitation methods. A challenging aspect of rehabilitation was that leaks through the lining were severe in the ventilation plenum where space is minimal and access difficult. A unique solution was to seal major leaks with polyurethane grout and manage the remaining leaks with a panning system and drainage improvements. The rehabilitation was successfully completed in 2005, with traffic maintained during construction.
2006
Clayton Mimura, PE
Geolabs, Inc.
Victor S. Romero, PE, CEG
Jacobs Associates