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Incorporating Spatial Heterogeneity in Stability Analyses of an Unsaturated Soil Embankment - Extended Role of Integrated Geophysics
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 25th European Meeting of Environmental and Engineering Geophysics, Sep 2019, Volume 2019, p.1 - 5
Abstract
Extreme climate events like frequent and heavy rainfall and extreme dry weather make slopes, dykes and embankments extremely vulnerable. The shallow subsoil in such cases are generally in unsaturated condition. In all common failure mechanisms of unsaturated slopes or embankments, the spatiotemporal distribution of water saturation and matric suction plays a crucial role. With input data from integrated geophysics, we have developed a new inversion scheme to invert in-situ soil-water characteristic curve (SWCC), linking saturation to suction. The new inversion uses total least squares to minimize the data-model residual simultaneously for water saturation, confining stress and smallstrain shear modulus. Applied to data obtained from integrated geophysics, the inversion offers quite accurate estimates for in-situ SWCC. For the first time, it has been possible to incorporate deterministically obtained heterogeneous SWCC to make reliable stability estimates for unsaturated slopes/embankments. For an embankment containing a clay layer underlying surficial silty-sand, the estimated factor of safety for Coulomb failure and internal erosion and piping can be dangerously overestimated if a mean value of SWCC is used, instead of a more accurate SWCC considering heterogeneity. For a clay-cored sand embankment, the mean value of SWCC can overestimate the safety factor.