Spatial variability: drained and undrained deviatoric load response

Abstract

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.

Determining an appropriate finite element size for modelling the strength of undrained random soils

“…Conversely, two points separated by a distance greater than h are largely uncorrelated. Many studies have been undertaken in recent years to develop probabilistic methods that address spatial variability in a systematic way (e.g., [9,19,11,13,14,16,1,21,18,17,20]). Of particular importance has been the development of the random finite element method (RFEM) for modelling the spatial variability of geomaterials (e.g., [7]).…”

On the estimation of scale of fluctuation in geostatistics

“…Vanmarcke (1984) and Wickremesinghe and Camapanella (1993) proposed an alternative method, based on the concept of variance function discussed in Vanmarcke (1977), which has been used in several studies (Jaksa, Kaggwa, and Brooker 1993;Hicks and Onisiphorou 2005;Lloret, Hicks, and Wong 2012;Lloret-Cabot, Hicks, and Nuttall 2013). Other techniques, combining random field theory with conventional approaches, have also been recently proposed (Kim and Santamarina 2008;Zhang, Zhang, and Tang 2008;Dasaka and Zhang 2012).…”

Sustainable development and energy geotechnology — Potential roles for geotechnical engineering

“…Consequently, their analysis must recognize the inherent spatial variability and scale-dependence in the subsurface, its anisotropy and associated emergent phenomena. Published numerical and experimental results have shown that spatial variability leads to the development of preferential conduction paths and a lower macroscale hydraulic conductivity, enhances the tendency to shear localization (even in contractive media), causes non-homogeneous stress and strain distributions, and results in media with lower stiffness (Jang et al, 2011;Kim and Santamarina, 2008). Future developments need to explore new field assessment methods and the development of robust procedures to take spatial variability into consideration during design.…”