REVIEW OF CPT DIRECT DESIGN METHODS FOR DRIVEN CAST-IN-SITU PILE CAPACITY USING INSTRUMENTED PILE LOAD TESTS TO FAILURE-Paper

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The paper evaluates cone penetration test (CPT)-based methods for predicting the capacity of driven cast-in-situ (DCIS) piles, a pile type for which published full-scale test data are limited. It analyses six sacrificial piles installed in Avonmouth, England, and loaded to failure, defined as pile-head settlement of 0.1 times the pile diameter. Four piles were instrumented to separate shaft and base resistance.<br /><br />The piles passed through soft estuarine clays into fluvial sands. Their capacities varied with the local sand profile and CPT cone resistance; greater embedment alone did not guarantee greater capacity. Instrumentation and load–settlement analysis showed that capacity was predominantly end-bearing, while shaft resistance mobilised earlier and then largely stabilised. Residual loads developed during installation and concrete curing, highlighting that resetting instruments before testing can distort interpretation—typically overestimating shaft resistance and underestimating base resistance.<br /><br />The study compared simplified and advanced CPT design methods. Predictions varied substantially: Fugro-05 overpredicted total capacity for all six piles, while most other methods underpredicted it. UWA-05 gave the closest and most consistent estimates of total capacity at failure, although it significantly overpredicted one potentially anomalous test. Fugro-05 best matched the separately measured shaft and base resistance components.<br /><br />The findings emphasise the importance of accounting for residual loads, local soil layering, weak lenses beneath the pile toe, and the CPT depth range used to estimate base resistance. The six tests also expand the publicly available DCIS database, supporting further assessment of design methods for this pile type.

Keywords

cone penetration test

CPT methods

driven cast-in-situ piles

DCIS piles

pile capacity

end-bearing resistance

shaft resistance

Avonmouth pile tests

residual loads

pile load settlement