Slopes and walls in Bognor Regis demand a rigorous understanding of the local ground conditions, where Cretaceous Upper and Lower Chalk formations are overlain by Quaternary drift deposits, including raised beach deposits, brickearth, and head. These variable strata, combined with the coastal proximity and fluctuating groundwater levels, create significant geotechnical challenges for both natural slopes and retaining structures. Our specialist investigation services, including comprehensive ground investigation and precise Cone Penetration Testing (CPT), are designed to characterise these materials in accordance with BS 5930:2015+A1:2020 and the requirements of the West Sussex County Council local planning authority.
Our methodology for slope stability assessment and wall design follows the Eurocode 7 framework, specifically BS EN 1997-1:2004+A1:2013 and the UK National Annex, employing Design Approach 1 for ultimate limit state verification. We quantify the effective shear strength parameters of the Chalk and overlying soils through a combination of In-Situ and advanced laboratory testing, critically evaluating the drained and undrained behaviour. The identification of low-strength layers within the brickearth or the presence of solution features in the Chalk is achieved using field density testing and detailed logging, providing essential inputs for analytical and numerical stability models compliant with CIRIA C760 guidance.
Typical projects in Bognor Regis range from assessing the stability of coastal cliffs along the Aldwick and Felpham frontages to designing embedded retaining walls for basement constructions in the town centre, where groundwater management is critical. We frequently investigate the condition of historic masonry sea walls and design soil nail or king post wall solutions for residential developments on sloping sites. A key part of these investigations involves a complete soil characterisation, including grain size analysis by sieve and hydrometer to classify the silty sands of the drift deposits, and Atterberg limits determination to assess the plasticity of the brickearth, which directly influences earth pressure calculations and the selection of appropriate foundations for any new wall structures.
The process begins with a phased ground investigation to develop a robust geotechnical model, progressing from desk study to intrusive works and finally to interpretive reporting. Deliverables include a factual report, a Ground Investigation Report (GIR) with detailed parameters, and a Geotechnical Design Report (GDR) containing fully verified slope stability analyses and wall designs with detailed construction drawings and specifications. Our value lies in delivering technically sound, economical solutions that mitigate the risks of ground movement and structural failure, ensuring long-term asset resilience against the aggressive coastal environment of Bognor Regis.