Soil behaviour across Cambridge varies dramatically depending on which side of the River Cam you are working on. The historic colleges and city centre sit predominantly on gravels of the First Terrace, which drain well and offer reasonably predictable bearing. Move east into the newer developments near Barnwell or south towards Trumpington and the clays of the Gault Formation dominate—sometimes stiff, sometimes surprisingly plastic after a wet winter. Without proper classification, assuming a uniform site can lead to serious misinterpretation of settlement potential. Our Atterberg limits testing programme quantifies the liquid limit, plastic limit and plasticity index of these cohesive deposits, giving engineers the data needed to predict volume change. When we encounter silty clay layers near the Backs, we often combine the analysis with a grain size distribution to distinguish true Gault from more recent alluvial silts that behave very differently under load. Cambridge’s building boom around the biomedical campus has pushed foundations onto marginal ground where this distinction matters more than ever.
A plasticity index above 25% in Cambridge’s Gault Clay signals active volume change potential—something no foundation design should ignore.
