Ground investigation in Portsmouth must address the complex coastal geology of the Hampshire Basin, where recent alluvium, raised beach deposits, and the underlying Bracklesham Group strata create variable bearing conditions and potential for soft, compressible layers. Our work follows the requirements of Eurocode 7 (BS EN 1997-2) and the national application document, ensuring that site characterisation for the city’s harbour and urban areas correctly identifies risks such as tidal groundwater and buried channels. A CPT campaign provides continuous profiling of these sequences, sharply defining transitions between estuarine clays and denser sands.
Portsmouth’s waterfront redevelopments, coastal defences, and infrastructure upgrades demand detailed factual and interpretative reports to underpin safe foundation design and earthworks. We routinely combine cone penetration testing with laboratory analysis to derive the strength and consolidation parameters needed for piled quay walls, flood alleviation schemes, and high-rise structures on reclaimed land. This integrated approach delivers the geotechnical model with the confidence required for construction in a dynamic tidal setting.
Ground investigation in Portsmouth demands a thorough understanding of the city’s complex coastal geology, which is dominated by the Lambeth Group deposits, the Cretaceous White Chalk Subgroup, and extensive superficial layers of Brickearth and Quaternary gravels. A robust geotechnical investigation is not merely a preliminary step but a critical risk management tool mandated by UK standards including BS 5930:2015+A1:2020 and the Eurocode 7 framework (BS EN 1997-2:2007). The proximity to the Solent introduces challenges of tidal influence, soft alluvium, and potential aggressive ground conditions, making it essential to characterise the stratigraphy accurately before any intrusive design work begins. Our approach integrates Cone Penetration Testing (CPT) with high-quality sampling to bridge the gap between empirical data and precise soil classification, ensuring compliance with the Portsmouth City Council planning requirements.
The methodology we employ is strictly aligned with the UK Specification for Ground Investigation, second edition, and relevant parts of the Manual of Contract Documents for Highway Works (MCHW). We typically progress from a phased desk study directly into intrusive fieldwork, which combines dynamic sampling and rotary core drilling with advanced In-Situ techniques. In granular soils where standard penetration tests (SPTs) may be unreliable, we utilise CPTs to provide continuous profiles of cone resistance and sleeve friction, correlating the data using Robertson’s chart to identify soil behaviour types. To verify on-site compaction and the density of granular fills, we frequently deploy the sand cone density method, a definitive and standardised approach for field density testing that remains a benchmark for earthworks validation in the UK.
Portsmouth’s construction landscape presents unique challenges, from the historic dockyard and coastal defence structures to the burgeoning residential developments on brownfield sites along Portsea Island. Investigations for low-rise housing often focus on the collapse potential of the Brickearth deposits, while marine projects require a detailed assessment of scour potential and the chalk bedrock’s variable weathering grade. For infrastructure projects, particularly those involving deep foundations, we move beyond index testing to measure specific engineering parameters. Our laboratory testing suite in Portsmouth is calibrated to handle these local soils, providing critical data on shear strength and consolidation. By applying rigorous classification protocols, we ensure that every parameter fed into the geotechnical interpretive report is representative of the ground’s true in-situ behaviour.
The investigative process culminates in a factual report that presents all borehole logs, CPT profiles, and in-situ test results, followed by a comprehensive Geotechnical Interpretive Report (GIR) that forms the basis for safe and economical design. The key deliverables include the quantitative characterisation of fine-grained soils through Atterberg limit testing to assess plasticity and volume change potential, alongside particle size distribution analysis using sieving and sedimentation hydrometer methods to precisely classify granular materials. This seamless integration of field data with UKAS-accredited laboratory testing provides designers with the reliable soil parameters required for foundation design, dewatering strategies, and earth retention. The ultimate value lies in de-risking the project by eliminating geological uncertainty, preventing costly over-design, and ensuring that the foundation solution is perfectly adapted to the specific ground conditions of the Portsmouth locale.