Initial tests on reversed open filters on sand-covered rock mounds

Initial tests on reversed open filters on sand-covered rock mounds

van de Ven, Daan (Student TU Delft; Van Oord)
Hofland, Bas (TU Delft Hydraulic Structures and Flood Risk)
van Kester, Dennis (Van Oord)
Smith, Greg (Van Oord)
Antonini, A. (TU Delft Coastal Engineering)

2023

When constructing land reclamations, often sand is placed on top of the coarse rock of the bund surrounding the reclamation. The use of a geometrically open filter between the interface of sand and rock could be cost effective. It is expected that even a geometrically open filter with sand on top of gravel might be stable due to the arching mechanism. For such a “reversed” open filter the actual stability is unknown. Hence this study focusses on the stability of a reversed geometrically open filter under cyclic loading. This paper mainly describes the development of the test setup. First the numerical model OpenFOAM was used to extract the gradients from a representative case study. Next a test setup was developed to generate these low-magnitude loads at full-scale. Various sand-filter combinations were tested, with a range of ratios of the diameters of the gravel filter (D15F) and the sandy base layer (D85B) and sand with a unimodal distribution. They were tested for both parallel (i//) and perpendicular (iꞱ) gradients. The order of magnitude of the occurring gradients obtained with the numerical model for the case-study were a parallel gradient of i//,2% ≈ 1%, decreasing to 0 going downward, and a rather constant perpendicular gradient of iꞱ,2% = 0.2-0.3 for the lowest 4 m of the reversed granular filter. The critical perpendicular gradients were estimated at iꞱc ≈ 0.2 to 0.1 for filter ratios of D85F/D15B = 7.5 to 9.5. The critical parallel gradients were measured at i//c ≈ 2% down to 1%, but might be influenced by simultaneously occurring perpendicular gradients. Even though for the test case no stable situation could be proven with respect to the perpendicular gradient, realistic situations with stable reversed open filters seem possible.

http://resolver.tudelft.nl/uuid:0b831a5b-e551-4f03-8c58-4e1f3f0efa65

Institution of Civil Engineers

2023-10-27

Procedings ICE Breakwaters conference 25-27 April 2023

ICE Breakwaters 2023, 2023-04-25 → 2023-04-27, Portsmouth Marriott Hotel, PO6 4SH, Portsmouth, United Kingdom

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

conference paper

© 2023 Daan van de Ven, Bas Hofland, Dennis van Kester, Greg Smith, A. Antonini