The Cran experimental site in Brittany: 50 years of geotechnical investigations and on site testing

For more than 50 years, the Cran experimental site in Brittany, France, has been dedicated to the study of very soft clay soils for a better understanding of the response of geotechnical structures in these soils, as well as to develop various sampling methods, in situ tests, and test protocols. As such, it has been the subject of several geotechnical investigation campaigns, supplemented as and when new technical advances and validation requirements arise. This paper presents the multiple test campaigns carried out; the results obtained in situ using pressuremeter, Cone Penetration Test, Dynamic Penetration Test, and Standard Penetration Test, as well as some geophysical tests; and the results achieved in the laboratory using triaxial tests in drained or undrained conditions, oedometric compression tests with radial or vertical drainage and with specific creep load steps, and others. It also presents the complete results of full-scale tests carried out on footings, piles, and bridge abutments on this experimental site. Finally, a complete synthesis of all accumulated data is presented, making it possible to characterize the homogeneity of the site, as well as the correlations that exist between the various strength and deformability parameters, and to compare the behavior of real structures with those expected by the investigation tests performed.