Subsidence of Granular Scour Protection around a Pile Exposed to Currents

Publikation: Beitrag in Buch/Bericht/Sammelwerk/KonferenzbandAufsatz in KonferenzbandForschungPeer-Review

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Details

OriginalspracheEnglisch
Titel des SammelwerksCoastal Structures 2019
Herausgeber/-innenNils Goseberg, Torsten Schlurmann
ErscheinungsortKarlsruhe
Seiten608-619
ISBN (elektronisch)978-3-939230-64-9
PublikationsstatusVeröffentlicht - 2019

Abstract

Comprehensive hydraulic model tests were carried out to obtain further insights into the winnowing mechanism within granular scour protection and to provide additional datasets for a holistic approach on the sinking of granular scour protection into the seabed. The tests focused on a) the initiation of erosion of bed material beneath the scour protection and on b) the depth as well as the
extend of the subsidence of the scour protection exposed to unidirectional current flow. The tests were conducted in a closed-circuit flume driven by a pump system and equipped with a sediment pit. In the center of the sediment pit, a transparent pile was installed to mimic a monopile structure. Surrounding
the pile, loose riprap materials were placed on top of the sand as scour protection. Thereby, the top level of the scour protection was constructed flush with the surroundings. As armor layer stones, three different stone gradings with median stone diameters between 13.0 – 44.0 mm were used. The winnowing process was monitored by a camera system placed inside the transparent pile and bed topography measurements by means of a laser distance sensor were carried out to determine the spatial extent of the subsidence. Critical flow velocities for the initiation of the winnowing process were found to increase with increasing layer thickness of the scour protection. On the other hand, critical flow velocities decreased with growing stone diameter. Final sinking depths were influenced by the flow velocity, the thickness of the scour protection and the grain size ratio. As expected, a larger flow velocity led to an increased sinking depth. Exposed to a strong current, a large horseshoe
vortex will form at the upstream side of the pile, increasing the capacity to transport sediment from beneath the scour protection. However, a large scour protection thickness reduces the sinking depth by dampening the horseshoe vortex before reaching the underlying bed. Equations predicting the critical
flow velocity for the initiation of the winnowing process as well as final sinking depths in dependency to the scour protection thickness and grain size ratio are introduced.

Zitieren

Subsidence of Granular Scour Protection around a Pile Exposed to Currents. / Schendel, Alexander; Schlurmann, Torsten.
Coastal Structures 2019. Hrsg. / Nils Goseberg; Torsten Schlurmann. Karlsruhe, 2019. S. 608-619.

Publikation: Beitrag in Buch/Bericht/Sammelwerk/KonferenzbandAufsatz in KonferenzbandForschungPeer-Review

Schendel, A & Schlurmann, T 2019, Subsidence of Granular Scour Protection around a Pile Exposed to Currents. in N Goseberg & T Schlurmann (Hrsg.), Coastal Structures 2019. Karlsruhe, S. 608-619. https://doi.org/10.18451/978-3-939230-64-9_061
Schendel, A., & Schlurmann, T. (2019). Subsidence of Granular Scour Protection around a Pile Exposed to Currents. In N. Goseberg, & T. Schlurmann (Hrsg.), Coastal Structures 2019 (S. 608-619). https://doi.org/10.18451/978-3-939230-64-9_061
Schendel A, Schlurmann T. Subsidence of Granular Scour Protection around a Pile Exposed to Currents. in Goseberg N, Schlurmann T, Hrsg., Coastal Structures 2019. Karlsruhe. 2019. S. 608-619 doi: 10.18451/978-3-939230-64-9_061
Schendel, Alexander ; Schlurmann, Torsten. / Subsidence of Granular Scour Protection around a Pile Exposed to Currents. Coastal Structures 2019. Hrsg. / Nils Goseberg ; Torsten Schlurmann. Karlsruhe, 2019. S. 608-619
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