Non-Destructive Testing, Evaluation and Optimization of Existing Deep Foundations for Re-Use Along the East Coast-Article

Article

Pdf Summary

The paper describes a phased approach for assessing and reusing existing deep foundations during renovations, expansions, and conversions. Reuse can reduce costs and avoid the difficulties of demolition, particularly in dense urban areas and historic buildings, where records of existing foundations are often incomplete.<br /><br />The process begins with a desk study of available plans, construction records, soil investigations, and load-test data. A team of architects, structural and geotechnical engineers, construction managers, and specialist contractors then conducts targeted field investigations to confirm foundation type, condition, dimensions, and subsurface conditions. Interior drilling may be necessary where exterior access is restricted.<br /><br />Testing methods include non-destructive tests to estimate concrete strength and locate reinforcement; low-strain and parallel-seismic testing to assess pile integrity and length; and high-strain dynamic testing to estimate capacity. Full-scale pile-cap load tests can verify and sometimes increase assumed design capacities, but require careful bracing and shoring. Where existing foundations cannot support proposed loads, retrofit options include adding supplementary piles or transferring loads to deeper, higher-capacity foundations.<br /><br />Monitoring settlement and lateral movement helps the project team respond promptly to unexpected behavior. Three-dimensional laser scanning can document existing spaces, support construction planning, and provide a baseline for detecting deformation.<br /><br />Case histories from Florida and the New York metropolitan area show that testing sometimes justified substantial increases in allowable pile capacity, reducing the need for costly retrofit work. The authors emphasize selecting suitable, sometimes complementary, testing methods and balancing the extent of investigation against project risk and cost. Their central conclusion is that coordinated assessment, testing, and monitoring can make foundation reuse safer, more economical, and more efficient.

Keywords

deep foundations

foundation reuse

geotechnical investigation

pile testing

structural assessment

renovation

load testing

settlement monitoring

laser scanning

retrofit foundations