The process from design to execution of the foundations of Danube Bridge Vidin-Calafat (Bulgaria-Romania border) is summarised. The foundations are made of 2.0 m and 1.5 m diameter floating concrete bored piles. excavated mainly on Pliocene clay that is founded below alluvial strata or loessian soils with variable thickness around 20 m. For the design the focus was put on the triaxial and the pressiometric tests carried out inside investigating boreholes. To lower the safety factor and make more precise the pile lengths, several loading tests on trial piles were made (a total of 6 O-cell tests). This paper emphasizes specially the parameters deduced from these tests and its correlation with .the previsions based on design. From the analysis of the O-Cell Test results some conclusions were derived: the loading tests showed that the calculus parameters derived from the tests were placed between those obtained from the triaxial tests and from the pressiometric tests; and that the ultimate values from loading tests matched to the limiting values established in the specialized literature and common standards for overconsolidated clays.