In Cardiff, the geology shifts noticeably between the reclaimed land of Cardiff Bay and the stiffer glacial tills found to the north. Many times we see structures on the former docklands suffer measurable differential settlement where fill thickness varies by less than two metres over the site. A thorough differential settlement analysis in Cardiff accounts for these abrupt changes in compressibility, using data from boreholes and CPT soundings to model the expected movement. Without this study, a building on the softer alluvium near the Taff can tilt several centimetres more than its neighbour on the buried terrace gravels. The team cross-references soil profiles with ensayo CPT logs to detect thin, compressible layers that would otherwise be missed in routine sampling.
A peat lens only 1.2 m thick can double the predicted differential movement at the surface if load eccentricity is not accounted for.