This paper presents the case of a hangar that was built in an embankment having 2000 m² and 6 m high. The subsoil is formed by a layer of organic clay and peat having 12 m of thickness. The hangar was constructed without knowing the bearing capacity and compressibility parameters of the clay under the embankment. The construction started with the ground being covered by a mixture of waste and remains of others constructions. A retaining wall of gabion was executed having 3 to 6 m of variable height in order to contain the embankment. During earthmoving operations, there was a slide in one corners of the ground and the soft clay and peat appeared upward. Several cracks were observed in the floor parallel to the retaining wall. Some fissures appeared in the masonry of the hangar. After some months later, the movement grew up accelerating and the complete ruin of the hangar occurred. The geotechnical characteristics of the clay deposit was made by borings (SPT), vane test and laboratory tests (oedometer and triaxial) in undisturbed shelby samples. The results of this investigation are presented as well as the back analysis of the failure.