Detection and quantification of sediment remobilization processes using a dynamic penetrometer

Stark, Nina; Kopf, Achim J

doi:10.23919/oceans.2011.6106914

Cited by 24 publications

(16 citation statements)

References 15 publications

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“…Such stratification can often be related to ongoing or recent sediment remobilization processes [22]. In Grand Passage some areas of bedrock were found covered with a thin layer of sand, gravel or shell fractures [10].…”

Section: Discussionmentioning

confidence: 99%

“…However, the free-fall penetrometer tests might make a smaller number of these more time-and cost-intensive tests possible. In addition, the small devices can also be deployed in the vicinity of the later installed structure, and would allow a monitoring of the development of seabed properties in comparison to the tests prior to installation [22].…”

Section: Discussionmentioning

confidence: 99%

“…Later such devices have proved particularly suitable for cost-and time-efficient geotechnical testing of the seabed surface in areas of difficult access and to investigate ongoing and recent sediment dynamics [9] [22]. These characteristics make these devices a promising technique for early site assessment in ocean renewable energy.…”

Section: A Portable Free-fall Penetrometersmentioning

confidence: 99%

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Cost-effective geotechnical and sedimentological early site assessment for ocean renewable energies

Stark

Hay

Trowse

2014

2014 Oceans - St. John's

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Soil mechanical properties of the seabed are related to a number of challenges in the development of ocean renewable energy. Early site assessment is an important part of the development of an ocean renewable energy project, and soil mechanical and sediment dynamical site characteristics should already be addressed at this stage. However, the suitability of the site for the installation of a ocean renewable energy converter (OREC) is still under evaluation and budgets are often strongly limited at this stage of the project. It follows that there is a need for cost-efficient survey strategies. Different methods have been tested in a tidal energy project in the Bay of Fundy, Canada, and a wave energy project in Yakutat, Alaska. Camera systems displayed sediment type, abundance of rocks, plants and small-scale bedforms. Portable free-fall penetrometers were deployed for testing of sediment strength and stratification at the uppermost seafloor. Areas of different sediment strength were identified, and loose, poorly compacted sediment layers quantified. Additionally, rocks and bedrock faces which were covered by a thin sediment layer and remained undetected by seafloor imaging sonars and grab samples, were found. Buried pressure sensors were used in preliminary experiments to monitor pore pressure variations with wave forcing and test the susceptibility to sediment liquefaction. First surveys using these methods attested that they deliver valuable information with regard to sediment and soil mechanical characteristics, while being deployable from local small fishery or harbor authority vessels. Availability of such vessels and devices is high, while purchasing/renting costs are rather low. This allows to perform such tests very cost-effectively, and thus provides a promising strategy for early site assessment in ocean structure engineering before larger budgets are available.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: A Portable Free-fall Penetrometersmentioning

confidence: 99%

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Cost-effective geotechnical and sedimentological early site assessment for ocean renewable energies

Stark

Hay

Trowse

2014

2014 Oceans - St. John's

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“…The dynamic CPTU probe is lowered through the water column in winch or free-fall mode, impacting the seafloor with an initial penetration rate (v 0 ) controlled by the weight of the device, buoyancy, winch speed or drag of the steel wire (e.g., see details in chapter 2.1 of Stark 2010). Penetration into the soil is driven by the momentum of the probe at a nonlinearly decreasing velocity, whereas the conventional, static CPTU instrument penetrates the soil with a constant penetration rate (v ref = 2 cm/s).…”

Section: Introductionmentioning

confidence: 99%

In situ dynamic piezocone penetrometer tests in natural clayey soils — a reappraisal of strain-rate corrections

SteinerAlois

KopfAchim

L’HeureuxJean-Sebastien

et al. 2014

Can. Geotech. J.

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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...

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“…The penetrometer impacts the soil at an initial impact velocity which depends on the probe's terminal free fall velocity in water and rope drag (Stark and Kopf ). Upon impact and during advancement through the soil, its deceleration is governed by the soil resistance against the probe.…”

Section: Methodsmentioning

confidence: 99%

Rapid sediment mapping and in situ geotechnical characterization in challenging aquatic areas

Albatal

Stark

2017

Limnology & Ocean Methods

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Yakutat Bay, Southeast Alaska, is characterized by significant spatial variations in sediment type and dynamics. The northwestern side is supplied by sediments from the nearby glaciers, and is affected by longshore sediment transport processes, while the southeastern side has no direct sediment input, and is affected by human activities. In situ seabed investigations can be difficult, and expensive, due to logistical challenges in such remote locations. A portable free fall penetrometer (PFFP) was deployed 149 times along 16 transects in water depths of 2–48 m. The deceleration and pore pressure records during the probe's penetration into the seabed were used to characterize the surficial sediments. Equivalents of quasi‐static bearing capacity were determined using the deceleration‐depth signatures, and yielded strong variabilities ranging from 5 to 107 kPa at sediment depths of 10.3–41.9 cm. Correlating the PFFP results to visual field observations and literature, a regional classification scheme, and an updated sediment distribution map were derived. The pore pressure response was correlated to the different sediment types, and was used to assess the sediment's consolidation state. At the northwestern side, an increasing pore pressure trend indicated underconsolidated cohesive sediments. At the southeastern side, clayey sediments appeared to be more consolidated except of sediments of high organic content near the populated areas. The use of the pore pressure measurements represents a novel way for rapid sediment characterization using PFFP. The presented approach to create rapidly a regional sediment classification scheme offers a time‐ and cost‐effective method to derive seabed sediment maps in areas of difficult access and logistics.

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Detection and quantification of sediment remobilization processes using a dynamic penetrometer

Cited by 24 publications

References 15 publications

Cost-effective geotechnical and sedimentological early site assessment for ocean renewable energies

Cost-effective geotechnical and sedimentological early site assessment for ocean renewable energies

In situ dynamic piezocone penetrometer tests in natural clayey soils — a reappraisal of strain-rate corrections

Rapid sediment mapping and in situ geotechnical characterization in challenging aquatic areas

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