A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Civil Engineering

Thesis (M. Sc.) - Asian Institute of Technology

Applicability of a new model for stress-strain non-linearity behavior of geomaterials, Double Exponential Fitting Model (DEFM), is studied in depth by examining its modelling capability of fitting the observed experimental data of various geomaterials over a wide range of strain. The detailed examinations are made for the results of UC and CU tests of three geomaterials, cement-treated sandy soil, mudstone and reconstituted clay. The emphasis of examination is laid on the influence of the known points on the determination of model parameters together .lwith the fitting accuracy. Similar examination is also made for the comparison ofDEFM with other existing models. The appraisal of the fitting is carried out in a quantitative manner. The results show that DEFM is effective in modelling non-linear behaviour of different geomaterials over a wide strain range in both stiffness-stress relationship and stress-strain relationship as long as the known fitting points are appropriately selected. Some criteria for choosing the fitting points in both two point fitting method and three-point fitting methods are proposed. The application of DEFM to the behaviour of stiffer geomaterials show higher degree of the fitting accuracy than those for softer geomaterials. It is found that DEFM is advantageous in modelling non-linear stress strain behaviour of geomaterials over a wide strain range as compared with other existing models.