In London, ground investigation is shaped by the variable geology of the Thames Basin, from river terrace gravels to the stiff London Clay Formation, with compliance driven by BS 5930 and Eurocode 7. A robust site assessment typically begins with an exploratory test pit to inspect shallow strata and identify obstructions, followed by standard penetration tests to log soil consistency and retrieve disturbed samples at depth.
This phased approach supports foundation design for basements, high-rise developments, and infrastructure near existing assets. For soft alluvial soils or liquefaction-prone fills, the cone penetration test delivers continuous, high-resolution profiling of undrained shear strength and soil behaviour type, enabling safe geotechnical recommendations without excessive conservatism.
Ground investigation in London is the systematic assessment of subsurface conditions to inform safe, efficient foundation design and earthworks. The capital’s geology is remarkably varied, demanding a rigorous approach under British Standards. From the deep London Clay Formation and the Lambeth Group sands to the high-density Thanet Sand and the underlying chalk, each stratum presents distinct geotechnical challenges. A compliant investigation must address these complexities in accordance with BS 5930:2015+A1:2020, the UK code of practice for site investigations. Our work integrates proven methods like the Cone Penetration Test (CPT) with targeted physical sampling to build a reliable ground model, always considering the local sequence of river terrace deposits and made ground prevalent across the city.
A robust investigation strategy in the UK combines direct and indirect techniques to satisfy Eurocode 7 (BS EN 1997-2) requirements. In-Situ forms the backbone of data acquisition, with the Standard Penetration Test (SPT) providing disturbed samples and a direct indication of density and consistency within boreholes. This is frequently paired with advanced mechanical profiling, such as the Flat Dilatometer Test (DMT) to capture high-resolution stiffness and stress history data in near-continuous profiles, particularly effective within the London Clay. Where direct measurement of strength and deformation parameters is critical, the Ménard pressuremeter test (PMT) offers a precise in-situ stress-strain curve, delivering the key parameters for settlement analysis and pile design. This integrated methodology, supported by laboratory testing to BS 1377, ensures the interpretive report meets the stringent requirements of UK regulators and insurers.
London’s dense urban fabric and ambitious infrastructure projects shape the scope of site investigations. Deep basements in Westminster and the City require precise characterization of the London Clay’s swelling potential and the water pressures within the Lambeth Group sands. For major transport works like Crossrail or HS2 phase, continuous CPT profiling is essential for mapping geological variability and locating buried channel features. Residential developments on former industrial land demand a focus on the thickness and composition of made ground, often investigated with exploratory test pits to visually log near-surface obstructions and contamination. Similarly, infrastructure projects frequently require validation of compacted fill, achieved through a field density test (sand cone method) to ensure compliance with the Method Specification for earthworks.
The investigation process begins with a desk study and site reconnaissance, followed by the design and execution of a phased fieldwork plan. The primary deliverable is a comprehensive Geotechnical Interpretative Report, presenting a factual account of ground conditions, derived parameters, and clear recommendations for foundation selection, earth retention, and groundwater management. This report provides the certainty needed to de-risk construction in London’s challenging ground. By integrating a full suite of In-Situ with a deep understanding of the local geological and regulatory landscape, we transform raw data into a powerful design tool, enabling project teams to proceed with confidence and avoid costly unforeseen ground conditions.