When a site investigation in Cheltenham is planned to Eurocode 7 (BS EN 1997-2:2007), the Standard Penetration Test remains the backbone of subsurface characterisation. The town sits at the foot of the Cotswold escarpment, where the Charmouth Mudstone Formation and overlying Midford Sands create a complex transition from stiff overconsolidated clays to dense silty sands. In our laboratory, we find that coupling the SPT hammer energy with a precise understanding of the local Charmouth Mudstone—weathered to a stiff, fissured clay across much of the urban area—is what separates a conservative footing design from an over-engineered one. For deep foundations near the River Chelt corridor, where soft alluvium masks the bedrock profile, the CPT testing provides a continuous sleeve friction record that complements the discrete SPT N-values we obtain, particularly where the transition from granular to cohesive strata is gradual rather than abrupt.
In Cheltenham's Charmouth Mudstone, an SPT N-value of 20 at three metres depth is not just a number—it is the difference between a ground-bearing slab and a piled solution.
