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Relationship between resilient modulus and soil index properties of unbound materials

Çöleri, Erdem
In the mechanistic design approach, which has already been started to utilize in several countries, the variations in material properties are better taken into account based on fundemental engineering principles. Resilient modulus is the most important material property that is used in the mechanistic design since it describes the true martial performance of unbound pavement layers under traffic loading. In this thesis, the objective is to determine the resilient modulus, used in the mechanistic design of pavement structures, for the unbound material types used in Turkey and develop linear and nonlinear prediction models to determine resilient response of unbound layers based on soil index properties, California Bearing Ratio (CBR) and Light Falling Weight Deflectometer (LFWD) test results. Application of genetic algorithm and curve shifting methodology to estimate design resilient modulus at various stress states is also investigated using the test results for finegrained soils. Resilient modulus estimation for a constant stress state based on genetic algorithm and curve shifting methodolgy is quite promising for fine-grained soils since nonlinear constitutive models do not have the capability of representing resilient responses under different conditions. Furthermore, tree-based modeling is discussed as an alternative way to develop resilient modulus prediction models. The outcome of the study will be a basis for the performance based design specifications of flexible pavements.