Analysis of Bi-directional Static Load Tests on Large Barrettes-Video

Video Transcription

Video Summary

Ahmed Mufti, a geotechnical engineer with 39 years of experience and projects across seven countries, presents bidirectional static load testing of barrettes for a 365-meter, 105-story building in Dubai.<br /><br />He reviews conventional pile-testing systems and instrumentation, then explains the bidirectional test method, standardized in ASTM D8169. An embedded jack loads the pile upward and downward, enabling high-capacity testing with less external reaction equipment. However, the method does not directly reproduce a pile’s behavior under a load applied at the top, and interpreting results—especially correcting for elastic shortening and extrapolating load–displacement curves—requires careful analysis.<br /><br />The presentation covers strain-gauge measurements, calculation of shaft friction and end bearing, and conversion of test results into load–settlement curves and soil-response curves for design software. Mufti applies these methods to three tested barrettes, comparing measured behavior with modeled capacities and soil profiles.<br /><br />He proposes deriving soil-response curves from the corrected top-load test curve rather than directly from behavior measured at the jack level. He describes this as a new approach requiring further calibration. He concludes that conventional top-down testing remains preferable when feasible, while bidirectional testing is valuable when exceptionally high test loads are needed.

Keywords

geotechnical engineering

bidirectional static load testing

barrettes

ASTM D8169

pile testing

load-settlement curves

soil-response curves