Abstract:
Potomac Clays - Landslide Susceptibility and Design of Various Earthen Structures
Fairfax County, Virginia
 ECS Mid-Atlantic
Corey D. Mislinski, P.E.
Abstract:
Potomac Clays, prevalent in the Mid-Atlantic region, present unique challenges for infrastructure design and construction due to their over-consolidated nature and potential for shear strength conditions stemming from historic landslides. Undiagnosed or improperly addressed, these problematic soils have led to retaining wall, slope, and embankment failures. Analyzing past failures provides invaluable lessons for improving future geostructural design practices.
A large Fairfax County data center project, underlain by Potomac Clays, required extensive earthwork, with the cut/fill line traversing the diagonal of the building footprint. Two cut walls, reaching 22 feet tall and 250 feet long, were constructed for grade separation on the site's high side. On the low side, approximately 600 feet of cut walls, scaling up to 25 feet high with 3H:1V (horizontal to vertical) backslopes, were necessary. Additionally, a 100-foot long, 20-foot high reinforced soil slope was implemented in a cut-to-fill transition area.
A thorough geotechnical investigation, incorporating numerous borings and laboratory testing, was essential to understand the site's complex geology. Leveraging historical data and project-specific findings, various geostructural systems were designed to mitigate potential landslide failure mechanisms.
This presentation will examine the site's geology, the interpretation of gathered geotechnical data, and provide an overview of the design of each geostructural system against potential landslide failure mechanisms. The goal is to equip practitioners with knowledge applicable to the evaluation and design of similar projects confronting the challenges inherent to Potomac Clay environments. This project serves as a valuable case study for improving design methodologies and minimizing future failures in similar geological conditions.