Stress history in undrained shear strength assessment of natural soils: case of a sediment dam Available to Purchase

The accurate assessment of undrained shear strength in natural soils is essential, as these materials often form the foundation of critical geotechnical structures such as embankments, slopes, and dams. Their behaviour is complex, influenced by stress history, depositional environment, and over-consolidation ratio (OCR). Conventional analysis methods typically assume homogeneity and uniform stress conditions, which do not represent the variability of natural soils, particularly those of pleistocene origin, often leading to conservative or unreliable stability estimates. Cone penetration tests with pore pressure measurement have improved interpretation by indirectly capturing stress history and stratigraphic variability; however, challenges remain in consistently defining the transition between drained and undrained behaviour and in relating undrained shear strength to effective stress parameters. To address these limitations, this study proposes a methodological framework introducing sectorisation of undrained shear strength ratios, considering both OCR and in situ stress state. The approach was applied to a sediment retention dam, demonstrating practical value in capturing subsurface heterogeneity and refining soil behaviour interpretation. Results indicate improved accuracy in defining shear strength parameters, thereby supporting safer and more reliable geotechnical design in complex geological settings.