Pilot tunnels: contractor's position

This paper presents the contractor's view concerning the usefulness of constructing a pilot tunnel as part of the site investigation program and offers guidelines for evaluating its benefits. These benefits can be realized both prior to and during construction. They include furnishing information about the geology and its behavior, and facilitating design development and construction operations. Pilot tunnels are generally most useful in large projects with limited surface access, and where the geologic conditions are unfavorable. Depending on project conditions, the construction of a pilot tunnel can reduce bid contingencies up to 20% of the project cost.