Characterising the pre-failure deformation properties of geomaterials, Theme Lecture for the Plenary Session No. 1

Recent developments in the characterization of geomaterial prefailure deformation properties are reviewed, focusing on the data required to predict ground deformations and structural displacement at working loads. Descriptions are given of the deformation characteristics developed at very small to intermediate strains, of a variety of geomaterials, in testing using modern laboratory and field techniques. The relationships between static and dynamic experiments, between laboratory and field techniques, and between testing and field full scale behavior are discussed. Important features that are highlighted include: kinematic yielding, effects of recent stress-time history, anisotropy, structuration and destructuration, non-linearity by strain and pressure and effects of cyclic loading. Careful distinctions are made between elastic, plastic and viscous properties.