GROUND IMPROVEMENT IS RARELY A ONE-SIZED FITS ALL SOLUTION: A Case Study on Ground Improvement at a Pennsylvania Distribution Center Site-Paper

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The Olyphant, Pennsylvania, distribution-center site presented challenging conditions typical of former coal-mining land: up to 50 feet of uncontrolled mine spoil, abandoned underground workings, variable bedrock, and substantial trapped water after unusually heavy rainfall. The spoil contained moisture-sensitive fines, making excavation, compaction, and construction difficult. The project needed a cost-effective alternative to removing and replacing the large volumes of fill while meeting settlement and bearing-capacity requirements.<br /><br />Following supplemental investigations, the team adopted a combined ground-improvement strategy. Dynamic compaction was used across most of the site, while aggregate piers treated softer, looser, and saturated zones where dynamic compaction alone was unsuitable. Deep mine investigations identified areas requiring grouting, and a settlement-monitoring program tracked response to placement of up to 29 feet of structural fill.<br /><br />Dynamic compaction increased average Standard Penetration Test values in the upper 25 feet by 47%, from 17 to 25 blows per foot; the minimum value rose from 2 to 8. The work also lowered ground elevations by approximately 12–18 inches. Aggregate-pier testing met design performance requirements. Monitoring recorded about 1.8–2 inches of settlement, which largely stabilized within roughly 90 days. Approximately 30 cubic yards of grout were placed to address potential movement associated with abandoned mines.<br /><br />The project demonstrates that difficult sites often require multiple compatible techniques rather than a single standard solution. Thorough investigation, early collaboration among the design team, contractor, and specialty contractors, and careful attention to groundwater and safe working-platform conditions were essential to achieving a practical, successful design.

Keywords

Olyphant Pennsylvania

distribution center

coal mining land

dynamic compaction

aggregate piers

mine spoil

ground improvement

settlement monitoring

grouting

bearing capacity