Geotechnical services for three-level, 50-foot-deep excavation with combined footprint of approximately 250,000 square feet. 250,000 sf.

Weidlinger Associates provided geotechnical services for a 3-level, 50-foot-deep excavation, with a combined footprint of approximately 250,000 square feet. The firm's geostructural engineers designed and implemented a subsurface exploration program to assess subsurface conditions and performed various laboratory tests to evaluate soil properties; these included undrained triaxial, consolidation, and direct sheer tests. Samples from the upper portion of the boreholes were screened for environmental contaminants, and in-situ borehole permeability tests were conducted to estimate the permeability of subsurface materials. Finite-element analyses were used to design the underground structures. Weidlinger also determined the required foundation depths for slurry walls and drilled shafts, as well as estimated settlements. The firm prepared a geotechnical report, assisted with specification preparation, and provided consultation with the design team during design and construction.

Weidlinger also designed an instrumentation program to monitor deformations of existing structures and utilities, as well as ground movement and groundwater fluctuations during construction. During construction, Weidlinger's full-time field representative ensured smooth implementation of the drawings, plans, and specifications. The field representative reviewed construction submittals, provided field recommendations and design modifications, and evaluated the structure's overall performance on site to avoid costly time delays.

In addition, Weidlinger provided Antiterrorism Force Protection protective design services that satisfy the Architect of the Capitol and the Capitol Police design criteria. The firm assisted the government in developing appropriate threat criteria and designed the critical structural and facade elements to resist the specified blast loading and ground shock loading for this below-grade visitor center. Included in the protective design were debris catch systems for two large skylights at the plaza level, the blast-resistant design of the visitor screening areas, loading docks, and entrances.

Completion Date: 2005
Location: Washington, DC
Owner or Client: Architect of the Capitol
Prime Consultant(s): RTKL Associates