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Cone penetration testing with pore pressure measurement (CPTU) is a cost-and time-efficient way of collecting in situ geotechnical parameters of near-surface marine soils for cable and pipeline tracks, offshore foundations, and geohazard identification. The measured dynamic CPTU parameters (cone penetration resistance, sleeve friction, pore pressure) are higher than the measured static CPTU parameters. This mismatch is caused by the different penetration rates used for dynamic and static CPTU tests (dynamic tests have up to 500 times higher penetration rates than the static tests; i.e., with the commonly used 2 cm/s penetration rate). This study presents comprehensive Calypso piston and gravity core as well as dynamic and static CPTU datasets acquired in the landslide-prone Sørfjorden area (Finneidfjord, northern Norway). The fjord-marine sediments at the study site are characterized as normally consolidated to slightly over consolidated clay-dominated soils with embedded layers of sandy silt to sand. The dynamic CPTU results were corrected to match the nearby static CPTU (i.e., distance less than 10 m) using strain-rate factors (SF) derived from three known correction methods. Based on a statistical test and visual comparison of dynamic and static CPTU profiles, the modified inverse sin-hyperbolic correction method is found to be best suited for the strain-rate correction of dynamic CPTU tests, and results in SF less than 1.35 for the corrected cone penetration resistance and up to 2.4 for the sleeve friction. Our data illustrate a positive correlation between penetration rate and penetration depth, which is governed by the consolidation state of the clays. The good agreement between SF-corrected dynamic CPTU data from 34 deployments (acquired within less than 36 h shiptime) with data obtained from static CPTU and laboratory experiments on sediment cores further demonstrates that the MARUM dynamic CPTU device is a powerful tool for characterizing the properties of surficial seafloor sediments in shallow-water environments.Key words: dynamic cone penetration testing with pore pressure measurement (CPTU), static CPTU, clayey soils, in situ comparison, Finneidfjord, weak layer, strain-rate effect, soil-specific rate coefficient.Résumé : L'essai de pénétration du cône avec la mesure des pressions interstitielle (CPTU) est une façon efficace d'un point de vue temps et coûts pour récolter des paramètres géotechniques in situ de sols marins près de la surface pour des applications comme le placement de câbles et pipelines, les fondations en mer et l'identification des risques géotechniques. Les paramètres dynamiques CPTU mesurés (résistance à la pénétration du cône, friction de l'enveloppe, pression interstitielle) sont supérieurs aux paramètres statiques CPTU mesurés. Cette différence est due aux taux de pénétration différents qui sont utilisés pour les essais dynamiques et statiques de CPTU (les essais dynamiques ont des taux de pénétration jusqu'à 500 fois plus élevés que les essais statiques, par exemple un taux de...

A combination of a dense reflection seismic grid and up to 50‐m‐long records from sediment cores and cone penetration tests was used to study the geometry and infill lithology of an E–W‐trending buried tunnel valley in the south‐eastern North Sea. In relation to previously known primarily N–S‐trending tunnel valleys in this area, the geometry and infill of this 38‐km‐long and up to 3‐km‐wide valley is comparable, but its E–W orientation is exceptional. The vertical cross‐section geometry may result from subglacial sediment erosion of advancing ice streams and secondary incision by large episodic meltwater discharges with high flow rates. The infill is composed of meltwater sands and reworked till remnants on the valley flanks that are overlain by late Elsterian rhythmic, laminated, lacustrine fine‐grained sediments towards the centre of the valley. A depression in the valley centre is filled with sediments most likely from the Holsteinian transgression and a subsequent post‐Holsteinian lacustrine quiet‐water setting. The exceptional axis orientation of this tunnel valley points to a regional N–S‐oriented ice front during the late Elsterian. Copyright © 2012 John Wiley & Sons, Ltd.

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12Altered pyroclastic (tephra) deposits are highly susceptible to landsliding, leading 13 to fatalities and property damage every year. Halloysite, a low-activity clay mineral, is 14 often associated with landslide-prone layers within altered tephra successions, especially 15 in deposits with high sensitivity, which describes the post-failure strength loss. However, 16 the precise role of halloysite in the development of sensitivity, and thus in sudden and 17 unpredictable landsliding, is unknown. Here we show that an abundance of mushroom-18 cap-shaped (MCS) spheroidal halloysite governs the development of sensitivity, and 19 hence proneness to landsliding, in altered rhyolitic tephras, North Island, New Zealand. 20We found that a highly sensitive layer, which was involved in a flow slide, has a 21 remarkably high content of aggregated MCS spheroids with substantial openings on one 22 (disaggregated) samples showed that the observable mushroom-caps were much more 131 abundant in the remolded samples, increasing from 4.4 ± 3.2% to 44.9 ± 11.6%. 132 ATTRACTION-DETACHMENT MODEL FOR FLOW SLIDING IN ALTERED 133 TEPHRAS 134The open-sided, mushroom-cap-shaped halloysite morphology has not been 135 reported previously. Because this particular morphology overwhelmingly occurs in the