ABSTRACT
Soil properties of both natural deposit or manmade fills are inherently variable in space. However, in geotechnical practice, the assumption of homogeneity within individual material zones is almost invariably introduced to simplify analysis. This study demonstrates the application of a stochastic approach to model random soil heterogeneity and to investigate its influence on hydraulic properties by analysing the case of seepage through a flood defence embankment with a random spatial distribution of porosity. In particular, a dependency on porosity is introduced inside the van Genuchten model, which is then used to describe water retention and permeability in the unsaturated domain. A Monte Carlo analysis is undertaken by using the finite element program CODE_BRIGHT to predict seepage through embankments with different random porosity fields. The study demonstrates that flow within a heterogeneous soil mass shows a preference to follow more porous paths. As a result, the unrealistic assumption of material homogeneity can lead to over-prediction of the time to reach steady state and under-prediction of the corresponding total flow rate across the embankment during wetting from an initial unsaturated state.
