A geotechnical stratigraphy for the shallow subsurface in the Southern Central Graben, North Sea

The Integration of conventional 3D seismic data with high-resolution 2D seismic data and cone penetration test (CPT) data from geotechnical jack-up foundation reports has enabled a new late Quaternary geotechnical stratigraphy for the Southern Danish Central Graben area in the North Sea. The shallow subsurface has been subdivided into geotechnical units based on seismic appearance and soil behaviour type. The lateral thickness and geotechnical property variations have been mapped and associated with the existing stratigraphies from adjacent areas in the German and British sectors. The geotechnical variations have also been related to geomorphological features in the subsurface that are a result of the changing glacial conditions over the last 120.000 years. Particularly, buried valleys produce unpredictable geotechnical conditions that require additional evaluation and possibly borehole investigations as well as CPTs. The study synthesizes data from multiple geotechnical surveys and extrapolates the local knowledge from the different sites, providing a better regional understanding of the geology and the geotechnical behaviour of the shallow subsurface.