Spatial variability: drained and undrained deviatoric load response

Geotechnical properties vary in space. Geostatistical parameters such as the mean, the standard deviation and the correlation length are characteristic for each sediment and formation history. The effects of spatial variability on the drained and undrained shear response of soils are investigated using numerical parametric studies where multiple realisations are tested for selected geostatistical parameters. Results show that the mean undrained shear strength decreases as spatial variability and correlation length increase. Spatial variability prompts strain localisation along neighbouring weak zones under both drained and undrained loading. Heterogeneous contractive media show internal homogenisation during drained deviatoric loading, and the drained shear resistance evolves towards the critical state; media with higher variability and longer correlation length require higher strain to attain internal homogenisation. Anisotropy in spatial correlation causes anisotropy in shear strength. An intermediate drainage condition emerges in spatially varying media whereby local drainage may develop during globally undrained shear; local drainage affects the load–deformation response.