The main focus in this thesis was understanding the behaviour of the subgrade (foundation ground or caping layer of the embankment) under infrastructure objects, as this directly affects the performance of the pavement. The behaviour of the foundation ground is strongly influenced by the CBR (California Bearing Ratio) value, which can change over time due to changes in water content. The aim of the thesis was to demonstrate and analyse the changes in key subgrade material properties depending on water content. Variation of CBR values, unconfined compressive strength, and stiffness during unconfined compression tests on laboratory-compacted specimens of fine-grained soil at different initial water contents and densities was analysed. Additionally, the relationships between CBR values with and without inundation, as well as the relationship between CBR value and unconfined compressive strength or stiffness were also analysed. Empirical equations for estimating CBR values from field measurements of the dynamic deformation modulus were evaluated. Due to large differences in CBR values predictions, the use of empirical equations is not recommended.
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