Geotechnical Properties from Portable Free Fall Penetrometer Measurements in Coastal Environments
Reem Jaber, Nina Stark
Abstract
Coastal environments are characterized by a variety of sediment deposits with highly diverse geotechnical properties. Particularly in energetic coastal environments, sediment type and properties may vary on small spatiotemporal scales, limited previous information may be available, and sediment coring may be difficult. This study proposes a single data analysis framework to estimate geotechnical strength parameters in the uppermost layers of the seabed surface for a wide variety of sediment types from portable free fall penetrometer (PFFP) measurements without need for previous or complementary data. The framework builds on existing approaches and modifies and integrates them toward one universal analysis procedure. Target results are to distinguish sediment type, estimate relative density and critical friction angle for coarse-grained sediments, and undrained shear strength for fine-grained sediments. Data sets and sediment samples collected from seven different sites across the US served the validation and assessment of the framework. It was found that for the PFFP used a penetration depth less than 20 cm indicated coarse-grained sediments with a certainty of 96%, whereas a penetration depth greater than 25 cm was associated with fine-grained sediments with a certainty of 100%. Friction angles yielded a favorable match with laboratory triaxial and direct shear testing for the sand within ±1° and undrained shear strength values resulted in mismatches <10% of minivane shear results for most fine-grained sediments using cone factor of 10 for two groups of sediment strength-depth profiles. Higher mismatches observed for the third type of distinct profiles (up to 48%) suggested lower cone factors, likely related to a change in sediment properties.