Dulles International Airport Temporary Rock Excavation Support Design
Location
Dulles, Virginia
Client
Metropolitan Washington Airport Authority
Cherry Hill Construction, Inc.
Services Provided
Rock Fall Protection
Geologic Condition Evaluations
Construction Monitoring Services
Project Overview
Schnabel performed geological engineering studies and provided design calculations and drawings for temporary support of vertical rock excavations up to 50 feet high for the Inner and Outer Domestic Automated People Mover (DAPM) Tunnels and the East Tug Tunnel to pass under Taxiway F at Dulles International Airport. Schnabel developed a conceptual rock bolting and anchorage support system which included grouted strand anchors, split-set rock stabilizers, and rock face protection consisting of reinforced shotcrete and chain link mesh. Ground water levels were controlled by installing near-horizontal drains at the vertical excavation face that extend behind assumed failure surfaces.
To evaluate subsurface conditions at the planned tunnel excavation site, a review of available boring logs, seismic refraction survey results, and ground water elevation data was performed. In addition, measurements of rock mass discontinuities, including strike and dip measurements of bedding planes and joint fracture planes within siltstone bedrock materials exposed in site excavation, was performed to construct stereonet projections to estimate rock block sliding potential.
Construction monitoring and documentation was provided throughout construction of the tunnel excavation. Schnabel developed design modifications and supplements to address localized areas of poor rock conditions exposed in the excavation and changes to the excavation plans.
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