| Almost all natural soils are highly variable and rarely homogeneous. Soil heterogeneity can be classified into two main categories. The first category is lithological heterogeneity, which can be manifested in the form of soft/stiff small soil volumes embedded in a stiffer/softer larger media of different soil types. The second source of heterogeneity can be attributed to soil inherent spatial variability, which is the variation of soil properties from one point to another in space due to variation of deposition conditions and loading history.; The main objective of this study is to clearly understand the design consequences of soil heterogeneity and to investigate different ways to incorporate it into geotechnical engineering design framework. This has been applied to static problems, such as shallow foundation settlement, and dynamic problems, such as liquefaction assessment.; The effect of different types of heterogeneity on the macro behavior of soil under static loading has been investigated through deterministic numerical analysis with stochastic input soil parameters. A shallow foundation resting on heterogeneous soil media was adopted as a consistent example for demonstrating the influence of ground heterogeneity on static geotechnical field problems. In addition, co-depositional fine tailings - sand embankments were analysed to assess the impact of lithological heterogeneity on the stability of such innovative tailings disposal systems.; Dynamic problems have been addressed through analysis of well-documented case histories of potentially liquefiable sites in California, USA. Empirical techniques were adopted in the analyses of these sites. Cone penetration test (CPT) data recorded at these sites were used to identify different lithologies and to assess different elements of soil inherent spatial variability. These elements were applied to perform liquefaction analyses of these sites in a probabilistic analysis framework.; This research study indicated that the influence of soil heterogeneity on its engineering behavior is problem-dependent. Quantitative assessment of this influence can be obtained by separate comprehensive analyses of each geotechnical field problem. Using mean values of soil properties in deterministic geotechnical analyses was found to be on the unsafe (non-conservative) side. In addition, a list of characteristic risk-based soil parameters for different applications is provided for use in engineering design. |
