Comparison of rock-scour protection berm with a shallow foundation under seismic liquefaction

Xu, D. and Madabhushi, S. and Harris, J. and Whitehouse, R.J.S. (2024) Comparison of rock-scour protection berm with a shallow foundation under seismic liquefaction. In: 8th International Conference on Earthquake Geotechnical Engineering, 7-10 May 2024, Osaka, Japan.

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Offshore wind is an ever-growing industry that is key to the future of green energy generation. As new windfarms are built in both seismic and scour prone regions, such as East Asia and North America, there is a need to understand the behaviour of rock-scour protection under seismic liquefaction. Rock dump is a common method to both combat and remediate scour, a phenomenon whereby the redirected water currents from a foundation create vortices which wash away the seabed sediment surrounding the foundation. Rock-scour protection usually consist of a filter layer, smaller rocks to reduce rock-sediment penetration, and armour rocks, larger boulders that resist the force of water. Under seismic loading, loose seabed sand will liquefy and lead to the settlement of rock. However, there is very limited research in this area. This paper presents the results of two dynamic, saturated centrifuge tests. A comparison is made between the behaviour of a scour protection rock berm and a shallow foundation model that exerts a similar overburden stress on the seabed as the rock berm. The main aim is to compare the differences in behaviour between the continuum based shallow foundation model (in the form of an aluminium plate) and a particulate rock berm model. The results show that for small magnitude input motions, the settlement of a plate is greater than that of rock, however, for larger earthquakes, their settlements are comparable, with the plate foundation model settlement being a fraction smaller. This result suggests that some amount of seabed material ingress into the rock berm following liquefaction, leading to slightly larger settlements. These observations from the centrifuge tests can have implications in using continuum based finite element models to estimate liquefaction induced scour settlements. The results presented in this paper form part of a larger research project that investigates the behaviour of rock-scour protection under seismic liquefaction to better aid future design.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Centrifuge testing, liquefaction, offshore, scour protection, earthquake
Subjects: Coasts > General
Maritime > General
Divisions: Coastal
Depositing User: Helen Stevenson
Date Deposited: 20 May 2024 10:57
Last Modified: 20 May 2024 10:57

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