In-Situ across Portsmouth and the Solent region provides direct geotechnical parameters within the natural ground, avoiding the disturbance of sampling and transport. Local geology—commonly the London Clay Formation, Wittering Formation sands, and overlying Quaternary gravels—demands methods that capture true density and strength in place. All work follows BS 5930 and Eurocode 7 Part 2, ensuring ground models reflect site-specific conditions. We routinely perform field density test (sand cone method) to verify compaction in granular fills and subgrade, delivering immediate compliance data on Portsmouth’s variable made ground.
These tests underpin foundation design for coastal defences, port infrastructure, and residential developments on former industrial land. Road and utility trenching projects also rely on accurate in-situ density to sign off backfill layers. For a full assessment of bearing capacity, we combine density checks with plate bearing test and dynamic probing, building a reliable picture of soil stiffness and strength at depth. Every investigation is tailored to the specific ground challenges of the South Coast.
In-Situ forms the core of any robust geotechnical investigation in Portsmouth, directly assessing ground conditions without the disturbance associated with sampling. This approach is critical due to the city's complex geology, ranging from the chalk of Portsdown Hill to the soft alluvial clays, silts, and river terrace gravels of Portsea Island. A well-planned campaign integrates these tests to characterise the variable Wittering Formation and recent drift deposits, ensuring designs account for potential issues like chalk dissolution features or high groundwater tables. The resulting data provides a direct measurement of soil behaviour, essential for complying with UK regulatory frameworks and the LABC guidelines prevalent in the city's coastal and brownfield developments.
Our methodology strictly adheres to the relevant UK standards, primarily BS EN ISO 22476 for field testing, ensuring verifiable and repeatable results. The CPT (Cone Penetration Test) is a cornerstone technique in Portsmouth, providing continuous, real-time profiles of tip resistance and sleeve friction to identify thin soft clay lenses within the Bracklesham Beds without the need for boreholes. This is often supplemented by direct field density tests using the sand cone method on granular fill layers to verify compaction compliance with Specification for Highway Works (SHW) Series 600. All procedures are executed using calibrated equipment, with strict adherence to BS 1377 methods where applicable, guaranteeing the defensibility of the data for foundation design.
Typical projects in Portsmouth demand a tailored mix of in-situ techniques to manage the city's unique engineering challenges. For the redevelopment of former naval dockyards, we combine rapid CPT profiling to map contamination pathways with precise density testing on reclaimed ground. Coastal defence schemes along Southsea rely on our laboratory verification of in-situ strength parameters to predict erosion resistance in the Brickearth deposits. Whether it is a multi-storey structure on deep piled foundations or a residential extension on a raft, understanding the true in-situ state of the Lambeth Group clays is non-negotiable for managing volume change potential and avoiding costly over-design.
Our process delivers a clear, actionable ground model from the initial test pit logging to the final interpretive report. We move beyond raw numbers, correlating field test data with index tests from our laboratory, such as grain size analysis and Atterberg limits, to refine soil classification. The final deliverable provides Portsmouth's structural engineers and architects with a single, integrated document containing design profiles and geotechnical parameters, de-risking the project and providing the confidence needed to progress from planning to construction on time.