DFI / EFFC WORKING PLATFORM TASK GROUP - FIELD TEST RESEARCH STUDY FRS#1-PDF

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The DFI/EFFC Field Research Study FRS#1 evaluated four in-situ methods for assessing working platforms and subgrades across construction sites in Europe and the United States: the static plate load test (PLT), light weight deflectometer (LWD), Stitz dynamic probing light (DPL), and PANDA dynamic cone penetrometer (DCP). The study examined their practicality, ability to identify weak spots, ease of use, efficiency, and potential to estimate geotechnical properties.<br /><br />Each method has distinct strengths. PLT provides the most established measurements of static stiffness and load–settlement behavior, but is slow, labor-intensive, and requires a heavy reaction mass. LWD is portable, quick, and suitable for frequent checks of near-surface stiffness, though results are surface-sensitive and should be calibrated against PLT. DPL and PANDA provide depth profiles that can help locate layer boundaries and weak zones; their results depend on soil conditions, and penetration can be limited by dense or coarse material. Field experience also identified equipment and usability issues, particularly with PANDA’s automatic hammer.<br /><br />The tests produce indicators—not direct measurements of ultimate bearing capacity. Correlations with design parameters such as strength, density, or compaction are empirical and can vary substantially with soil type, moisture, construction history, and test conditions. Field results showed considerable variability, including between nearby test points, and no universal conversion factor reliably linked dynamic and static measurements across all sites.<br /><br />The study recommends a combined testing approach: use a small number of PLTs as reference checks, LWD for rapid surface coverage, and DPL or PANDA for deeper profiling and thickness verification. Site-specific calibration, adequate test density, and interpretation alongside soil investigations are essential. Future research should develop stronger material-specific correlations, improve calibration datasets, and refine integrated testing and verification protocols.

Keywords

DFI

EFFC

Field Research Study

plate load test

light weight deflectometer

dynamic probing

PANDA

subgrade assessment

working platforms

geotechnical calibration