This paper describes a simple procedure for evaluating deformation behavior of clay foundation under embankment using the simplified method for determining the soil parameters estimated by plasticity index and elasto-viscoplastic model. In the present analysis, we used the in-situ data obtained by standard penetration test which is used worldwide in the economical Points of view to estimate the soil parameters and the stress state of the clay foundation. Reasonable agreements have been obtained between the measured and the computed values of the ground surface movements beneath the center and the shoulder of the embankment for the multi-soil layers. The predicted lateral deformation, however, overestimates the field measurements. Finally, the analytical results obtained by the present methods are found to be reasonable in the preliminary design, owing to idealizing assumptions and uncertainty in the data, therefore, it is encouraged to use the presented methods in engineering practice of embankment on normally consolidated cohesive soil stratum. The applicability of the present method to other fields will require further research.