Engineering Properties of Late Pleistocene and Holocene Sediments of the Continental Shelf Offshore Trinidad-Paper

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The paper presents a database of advanced geotechnical test results for Late Pleistocene and Holocene sediments in the Columbus Basin, offshore Trinidad, and compares them with published Gulf of Mexico and Bay of Campeche data. The findings are intended to support future offshore developments and reassessment of older platforms where site-specific data are limited.<br /><br />Sediments vary from clay to sand, often changing over short distances and containing small-scale inclusions that complicate comparisons between laboratory tests and index properties. Piezocone penetration testing (PCPT) detects this variability more consistently than laboratory sampling. The investigated soils are mostly Holocene to late Pleistocene in age; apparent overconsolidation in clays and dense sands may partly reflect historical wave and earthquake loading.<br /><br />Direct simple shear (DSS) tests indicate that Trinidad clay’s normalized undrained shear strength is broadly consistent with Gulf of Mexico clay. Its average normally consolidated strength ratio is about 0.26, and an overconsolidation exponent of 0.75 provides a useful characterization. Shear-rate increases produce scattered strength gains of 0–8% per logarithmic rate cycle above the reference rate. Drained triaxial tests yield sand friction angles generally between 30° and 45° (with a broader reported range of 26°–48°); ring-shear tests give a residual friction angle averaging 30.5°. Resonant-column and cyclic DSS results show modulus-reduction behavior comparable to, or slightly less than, published correlations.<br /><br />The authors recommend using these regional normalized properties alongside geological understanding and high-quality in-situ data to reduce redundant testing and improve interpretation of legacy measurements. They also caution that cone-based density estimates and liquefaction assessments may be misleading where cyclic loading and nonzero pore pressures affect sand response. Future investigations should integrate PCPT, seismic PCPT, and shear-wave velocity logging.

Keywords

geotechnical

Late Pleistocene

Holocene

Columbus Basin

offshore Trinidad

piezocone penetration testing

direct simple shear

undrained shear strength

sand friction angle

liquefaction assessment