Comparison of Rapid Load Test Analysis Techniques in Clay Soils

Michael J. Brown, John J. M. Powell

    Research output: Contribution to journalArticlepeer-review

    13 Citations (Scopus)


    Rapid load pile testing (RLT) techniques such as Statnamic were developed as an alternative to more frequently adopted static and dynamic tests. The existing unloading point method (UPM) for deriving equivalent static load-settlement behavior from rapid load tests seems to be adequate in coarse-grained soils but may result in poor prediction in clays and silts. To address these shortcomings, the UPM has been improved to reflect soil type, and new analysis techniques have been developed. To test the performance of the improved UPM and new analysis techniques, pile tests from two clay sites were analyzed. The first case study site was underlain by very to extremely high-plasticity Quaternary London clay, and the second site was underlain by low-to intermediate-plasticity matrix dominant glacial till. The best predictions of static equivalent load-settlement behavior for very-high-plasticity clay were obtained from a new analysis technique that incorporated a soil-specific rate effect parameter (selected on the basis of the clays' plasticity index) that varied with pile settlement. In general, the UPM performed better for tests undertaken in the low-to intermediate-plasticity glacial till, as there is greater experience of RLT in these soils. The results of the study suggest that the development of analysis techniques would benefit greatly from tests in a wider variety of soil types. On the basis of the findings of this study, improvements to the UPM and Schmuker techniques are presented, which include pile settlement-dependent variation of the damping and rate effect parameters. DOI: 10.1061/(ASCE)GT.1943-5606.0000733. (C) 2013 American Society of Civil Engineers.

    Original languageEnglish
    Pages (from-to)152-161
    Number of pages10
    JournalJournal of Geotechnical and Geoenvironmental Engineering
    Issue number1
    Publication statusPublished - Jan 2013


    • Static tests
    • Soil-pile interaction
    • PILE
    • Glacial till
    • Fine-grained soils
    • Pile load tests
    • Damping
    • Clays


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