Estimating Lateral Support Pressure for Rock Cuts at Washington-Dulles International Airport Expansion

Synopsis:

Washington-Dulles International Airport (Virginia, USA) has been expanding its capacity since 1999. This expansion has required extensive vertical, open-cut rock excavations to depths of up to approximately 20 m adjacent to existing infrastructure for construction of new below-ground stations for the new Automated People Mover (APM) passenger transportation system. As the construction could not impact the airport operations, the selection of support pressures for the rock excavations had to balance the projects’ risks and construction costs. Site investigation identified that bedding dipping at approximately 30° would be the primary hazard to the vertical rock cuts.

Extensive laboratory testing and field observations suggested that the potential for a large slide along a bedding plane was relatively low. Therefore, design lateral pressures for permanent station walls were based on a potential failure model of local wedge/block failure. The reduction in lateral support requirements for the permanent below-grade walls for the APM station structures resulted in significant cost savings to the project. Detailed field mapping combined with automated instrumentation were successfully used to confirm the design assumptions.

Estimating Lateral Support Pressure for Rock Cuts at Washington Dulles International Airport Expansion
First Canada – US Rock Mechanics Symposium Proceedings
May 27-31, 2007
Vancouver, British Columbia, Canada