CPT Data Showing Anomalies - Assessment and Potential Post-Processing-Paper

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Cone penetration tests (CPTs) are widely used in offshore soil investigations, but occasional data anomalies can create uncertainty in geotechnical design. This paper reviews common causes, their effects, how they may be recognised, and whether post-processing can reliably correct them.<br /><br />Examples include temperature differences between the cone and soil, temperature changes during penetration, loss of pore-pressure filter saturation, penetration of a seafloor template into soft seabed, incorrect zero offsets, force transfer between the cone and friction sleeve due to trapped soil, and errors in estimated depth or penetration rate.<br /><br />Temperature effects can substantially distort cone resistance, especially in weak soils and during transitions between warm seawater or drilling fluid and colder soil. Sleeve friction and pore pressure may also be affected, though often less. Current post-processing methods for temperature-related cone resistance anomalies are considered inadequate; prevention and mitigation—such as suitable deployment methods, pauses to allow thermal equilibration, or improved sensor technology—are preferable.<br /><br />Loss of filter saturation can produce strongly negative, sluggish pore-pressure readings, making those measurements unreliable and potentially affecting corrected cone resistance. Seafloor-template loading can alter shallow soil stresses or disturb the seabed, while incorrect zero offsets can materially affect shallow results. Cross-talk between cone resistance and sleeve friction may sometimes be identified from abnormal data patterns, but correction is generally not recommended.<br /><br />The authors emphasise that anomalies should be assessed using available records and complementary evidence, including other CPTs, laboratory tests, and in-situ investigations. Post-processing should be attempted only when justified, and corrected data must be clearly identified. In many cases, documenting and selectively disregarding unreliable data is more defensible than applying uncertain corrections.

Keywords

cone penetration test

CPT anomalies

offshore soil investigation

geotechnical design

cone resistance

pore pressure

temperature effects

filter saturation

data correction

seabed investigation