Cardiff's topography is more varied than many assume. The city centre sits on flat reclaimed land along the Taff estuary, but the northern suburbs climb into Carboniferous sandstone ridges. We see failure surfaces developing along clay seams within the Coal Measures strata. A proper slope stability analysis identifies these critical planes before any cut or fill operation begins. For projects in the Lisvane or Rhiwbina areas, we often combine limit equilibrium software with field data from ensayo SPT to constrain shear strength parameters. The groundwater regime near the Taff can shift rapidly after heavy rainfall, so we always model worst-case phreatic conditions. Our approach starts with a geological desk study and ends with a factor of safety calculation under Eurocode 7.
A 0.05 drop in factor of safety can be the difference between a stable slope and a costly failure.