Monopile response to scour and scour protection
<p>Scour of seabed sediments can occur around offshore structures, the resultant reduction in strength and stiffness of the structure’s foundations presents operational challenges for monopile-supported offshore wind turbine structures. Turbines are at risk of reduced operation or even prematu...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2019
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| _version_ | 1817932331345772544 |
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| author | Mayall, R |
| author2 | Byrne, B |
| author_facet | Byrne, B Mayall, R |
| author_sort | Mayall, R |
| collection | OXFORD |
| description | <p>Scour of seabed sediments can occur around offshore structures, the resultant reduction in strength and stiffness of the structure’s foundations presents operational challenges for monopile-supported offshore wind turbine structures. Turbines are at risk of reduced operation or even premature decommissioning if scour causes the natural frequency of a wind turbine to drop too close to the loading frequency, or if the foundation capacity is compromised. In practice scour protection systems are used to mitigate the development of scour itself. Scour protection may also have a restorative influence on the natural frequencies of the structure and capacity of the foundation. This portfolio presents the results of a DEng research project exploring the interactions between scour development, scour protection, foundation stiffness and strength, and structural dynamics of offshore wind turbine structures.</p>
<p>Flume experiments were performed, where a scale monopile – tower system exposed to realistic scour development in the Fast Flow Facility flume at HR Wallingford was subjected to structural dynamics testing and lateral loading. Three scour protection systems were modelled in the experiments: pre-installed rock-armour, remedial rock fill, and remedial tyre-filled net options.</p>
<p>Numerical modelling is presented, using a one-dimensional (1D) finite element model developed for the analysis of natural frequencies for monopile-supported turbines with scour and scour protection. A 1D finite element approach was also used to explore the results of the lateral loading experiments. The numerical modelling produces results that are consistent with data from the flume experiments and from a case study of field data from a high scour offshore wind farm.</p>
<p>The research confirms that there is potential for scour protection systems to enhance the stiffness and capacity of monopile foundations. These gains are negligible for tyre-filled net scour protection systems due to the low stiffness and density of the tyres. The stiffness contribution of rock-type scour protection systems is further enhanced if sand accumulates in the scour protection matrix, but these positive contributions become diminished if extreme global scour causes the scour protection to become unstable. Pre-installed rock armour scour protection systems provide the most reliable solution in terms of seabed stability and foundation response.</p> |
| first_indexed | 2024-03-06T20:04:40Z |
| format | Thesis |
| id | oxford-uuid:2886ac08-c59e-409d-8d60-6724443d8d1a |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:36:13Z |
| publishDate | 2019 |
| record_format | dspace |
| spelling | oxford-uuid:2886ac08-c59e-409d-8d60-6724443d8d1a2024-12-01T19:51:02ZMonopile response to scour and scour protectionThesishttp://purl.org/coar/resource_type/c_db06uuid:2886ac08-c59e-409d-8d60-6724443d8d1aEnglishORA Deposit2019Mayall, RByrne, BHeald, SBurd, HSheil, BMcAdam, RWhitehouse, RSlater, P<p>Scour of seabed sediments can occur around offshore structures, the resultant reduction in strength and stiffness of the structure’s foundations presents operational challenges for monopile-supported offshore wind turbine structures. Turbines are at risk of reduced operation or even premature decommissioning if scour causes the natural frequency of a wind turbine to drop too close to the loading frequency, or if the foundation capacity is compromised. In practice scour protection systems are used to mitigate the development of scour itself. Scour protection may also have a restorative influence on the natural frequencies of the structure and capacity of the foundation. This portfolio presents the results of a DEng research project exploring the interactions between scour development, scour protection, foundation stiffness and strength, and structural dynamics of offshore wind turbine structures.</p> <p>Flume experiments were performed, where a scale monopile – tower system exposed to realistic scour development in the Fast Flow Facility flume at HR Wallingford was subjected to structural dynamics testing and lateral loading. Three scour protection systems were modelled in the experiments: pre-installed rock-armour, remedial rock fill, and remedial tyre-filled net options.</p> <p>Numerical modelling is presented, using a one-dimensional (1D) finite element model developed for the analysis of natural frequencies for monopile-supported turbines with scour and scour protection. A 1D finite element approach was also used to explore the results of the lateral loading experiments. The numerical modelling produces results that are consistent with data from the flume experiments and from a case study of field data from a high scour offshore wind farm.</p> <p>The research confirms that there is potential for scour protection systems to enhance the stiffness and capacity of monopile foundations. These gains are negligible for tyre-filled net scour protection systems due to the low stiffness and density of the tyres. The stiffness contribution of rock-type scour protection systems is further enhanced if sand accumulates in the scour protection matrix, but these positive contributions become diminished if extreme global scour causes the scour protection to become unstable. Pre-installed rock armour scour protection systems provide the most reliable solution in terms of seabed stability and foundation response.</p> |
| spellingShingle | Mayall, R Monopile response to scour and scour protection |
| title | Monopile response to scour and scour protection |
| title_full | Monopile response to scour and scour protection |
| title_fullStr | Monopile response to scour and scour protection |
| title_full_unstemmed | Monopile response to scour and scour protection |
| title_short | Monopile response to scour and scour protection |
| title_sort | monopile response to scour and scour protection |
| work_keys_str_mv | AT mayallr monopileresponsetoscourandscourprotection |