Scira Offshore Energy Ltd (Scira) propose to construct and operate an offshore wind farm at the Sheringham Shoal Wind Farm location. The site is located approximately 17km to 23km offshore from the Norfolk coastal town of Sheringham and approximately 5km north of the offshore sand bank known as Sheringham Shoal. The development will comprise offshore wind turbines, meteorological mast and transformer platforms in water depths between 15m and 22m. A series of investigations have been performed including geophysical and geotechnical investigations. The geotechnical investigations have comprised shallow seabed vibrocores and cone penetration tests and composite boreholes to a maximum depth of 70m below seabed. It should however be noted the database of testing is sparse, with some inappropriate coverage of both seismic and boreholes. There is also limited quality seismic data at depth. This report has reviewed the available information and the data has been used to develop a ground model for the site. This work finds that the geology at the site comprises the following sequence of soils: 1. Holocene (recent) deposits – generally comprising a thin veneer of gravelly sand; 2. Bolders Bank Formation –predominately firm to stiff clay, typically 10 m thick; 3. Egmond Ground Formation – predominantly dense sand, approximately 5m thick; 4. Swarte Bank Formation – predominantly very stiff clay, variable thickness; 5. Chalk – unstructured occasionally structured chalk present at a variable depth across the site. The geotechnical data for the site has been reviewed and collated into the specific soil units. Based on this work, the variability in each soil unit has been assessed and geotechnical profiles are presented. The limited database has lead to coarse and uncertain interpretation and wide ranges for parameter values. To assist pile design, geotechnical design parameters have been presented for both best estimate conditions for geotechnical design and upper bound associated with assessment of pile driving for a series of representative design profiles. Specific pile sizes are not known at this stage, hence the output of this study is presented as a series of graphs to enable pile vertical capacity to be calculated and static resistance to driving (SRD) to be used to assist selection of appropriate pile hammers. p-y curves have been developed for input into appropriate pile analysis programmes to assist prediction of the response of the monopole foundation.
2007, SEtech (Geotechnical Engineers) Limited, Sheringham Shoal Offshore Wind Farm, Geotechnical Integration Study