Nicholson in the Neighborhood: Virginia's North Hill Project-PPT Presentation

PPT Presentation

Pdf Summary

The North Hill Project in Alexandria, Virginia, transformed a long-vacant 33-acre site into a residential development with multifamily housing, townhomes, and plans for a future park. Because the existing slope showed signs of instability, permanent earth-retention walls were needed to create usable land while preserving wooded areas, matching existing contours, and meeting architectural requirements. Wall movement was limited to a maximum of 2 inches.<br /><br />The site’s coastal-plain soils were highly variable, including plastic clays, silts, and sands, with slickensides, perched groundwater, and evidence of prior movement. These conditions complicated soil characterization and construction. Design addressed different soil strengths across construction, serviceability, and long-term conditions, and required a minimum global-stability factor of safety of 1.25.<br /><br />The project used large-diameter drilled soldier piles and high-capacity strand anchors bonded beyond potential deep failure surfaces. The multifamily wall extended about 800 feet, reached a maximum height of 15 feet, and was mainly cantilevered. The townhome wall was about 1,000 feet long and up to 40 feet high, with anchors across most of its length. Pre-production testing established anchor bond stresses.<br /><br />Construction encountered collapsing pile holes caused by perched water and running sands. Crews adapted by using temporary casing and then segmental casing. Anchors were drilled with temporary casing, grouted, and proof-tested; performance and extended-creep tests were also conducted. Architectural shotcrete provided the finished wall faces.<br /><br />The presentation highlights the importance of suitable backfill to wall movement and records construction methods and lessons learned. It does not provide specific final wall-movement measurements.

Keywords

North Hill Project

Alexandria Virginia

earth-retention walls

multifamily housing

townhomes

drilled soldier piles

strand anchors

coastal-plain soils

global stability

shotcrete