Problem of Uncertainties in Geotechnical Engineering
Different types of uncertainties are involved in the geotechnical engineering, for example, uncertainty of concept, uncertainty of material classification, soil parameters, constitutive or empirical models, boundary conditions, other uncertainty caused by
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Problem of Uncertainties in Geotechnical Engineering
1.1 Uncertainties in Geotechnical Engineering Different types of uncertainties are involved in the geotechnical engineering, for example, uncertainty of concept, uncertainty of material classification, soil parameters, constitutive or empirical models, boundary conditions, other uncertainty caused by measurement error, and so on. All these uncertainties affect the evaluation of the soil or structure performance, and they are required to be considered and analyzed for reliable evaluation results. According to the type of uncertainty, different analysis methods have been utilized to evaluate the uncertainty, for example, stochastic theory, fuzzy mathematics, theory of gray systems, artificial neural networks, genetic algorithms, and so on. In some cases, these methods are coupled to solve the uncertain problems. Among these methods, the probabilistic method in stochastic theory has been widely applied to many aspects of geotechnical engineering, for example, slope analysis [1–4], liquefaction analysis [5, 6], reliability analysis of reinforced embankment [7], seepage analysis [8], soil–water characteristic curve [9–11], reducing uncertainties in empirical correlations [12], and so on. In the following sections, the sources of uncertainty and their analysis methods for predicting the performance of soil or structure are reviewed.
1.1.1 Uncertainties in Soil Properties Soils are porous and discontinuous media and they are formed by the weathering of rocks. Under the natural conditions, the state of soil is affected by various factors, for example, stress level and stress history, water seepage, physical and chemical changes. Even in the homogeneous soil, the soil property also varies with the site, and it possesses the spatial variability. Due to these characteristics of soil, there are inevitable uncertainties involved in the determined soil properties. The uncertainties in measured soil properties are associated with the soil sample disturbance, test © Tongji University Press 2021 W. Zhou et al., Practice of Bayesian Probability Theory in Geotechnical Engineering, https://doi.org/10.1007/978-981-15-9105-1_1
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1 Problem of Uncertainties in Geotechnical Engineering
conditions, human factors and statistical uncertainties. The uncertainties of estimated soil properties by models are caused by the limited test data of soil samples, the imperfection of adopted estimation formula and the uncertainty of other relevant soil properties. Tang [13] focused on the uncertainty characterization of soil properties in a homogeneous soil layer, and stated three main sources of uncertainties: inherent spatial variability, systematic uncertainties from the tests and estimation errors from insufficient samples. He also proposed a simplified method to incorporate these major sources of uncertainties in determining the statistic of the spatial average soil properties. Phoon and Kulhawy [14, 15] also summarized three primary sources for the geotechnical uncertainty: inherent vari
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