Pilot TunnelsThe Contractors' Position

ABSTRACT 
Geologic uncertainty in underground construction promotes design and construction conservatism and has a significant impact on project cost. Site investigation can reduce this uncertainty and decrease the contingency amounts included in bids. Pilot tunnels are one of the best geologic exploration methods but also one of the most expensive. This paper presents the contractors' 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, and 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.

AUTHORS 
Photios G. Ioannou
Civil & Environmental Engineering Department
University of Michigan
Ann Arbor, Michigan 48109-2125, U.S.A.
e-mail: photios@umich.edu


KEYWORDS 

Underground construction, tunneling, pilot tunnel, exploration, geology, subsurface investigation, tunnel support, excavation, contracts


AVAILABILITY 
Ioannou, P.G., "Pilot Tunnels—The Contractors' Position," Journal of Construction Engineering and Management, ASCE, Vol. 114, No. 4, 594-613, Dec. 1988.