COMPARISON OF DYNAMIC PROPERTIES OF CLAYS OBTAINED BY DIFFERENT TEST METHODS

For cohesive soils, an attempt for the classification of Gmax considering two relevant parameters, namely confining pressure (σ0’) and plasticity index (PI), was carried out by hard k-means (HKM), fuzzy c-means (FCM) and Kohonen’s self organizing map (SOM) methodologies. After determination of descriptive statistics of the experimental data, three different methods were applied to determine the ranges as well as representative values of Gmax using the free parameters. The first part of the study is a description and the analysis of experimental investigations conducted to determine the nonlinear stress-strain behaviors of clays when subjected to cyclic loadings at small strain levels. A series of torsional shear and cyclic triaxial shear tests were performed under undrained conditions to analyze the variations in the stress–strain properties of undisturbed saturated clay samples consolidated to specified confining pressure. The uniform cyclic sinusoidal loading at a 0.1 Hz frequency was applied to samples with different confining pressures. Test results are presented and evaluated in detail. The second part of the study focuses on hard k-means (HKM), fuzzy c-means (FCM) and Kohonen’s self organizing map (SOM) techniques to classify the complex mapping ranging from plasticity index and confining pressure input spaces to dynamic shear modulus output space. Consequently, comparative results were presented in terms of the methods’ clustering capabilities, and the benefit of such an analysis in soil dynamics was evaluated. Results indicate that the dynamic properties of clays are significantly affected by the testing technique and the initial conditions.