3. In situ and laboratory soil characterization

The purpose of geological and geotechnical surveys is to acquire the data needed for the studies associated with the structures to be built. These surveys are more or less detailed, depending on the progress of the project.

Specific soil data are required to characterize site effects. These include :

• the shear wave velocity profile V _S measured, for example, by cross-hole tests, and the Poisson's ratio of the soil layers;

• curves showing the evolution of shear modulus G and damping D as a function of distortion γ, or the non-linear behavior of the soil ;

• the geometry of the sedimentary basin, where applicable.

Added to this is the stratigraphy of the site determined from...