From Ground Investigation to the Geotechnical Model in Structurally Complex Formations

When dealing with structurally complex formations, the definition of a reliable geotechnical model is often made difficult by the scarcity of undisturbed samples and by the erratic properties of the material. This is particularly true when the original formation suffered strong mechanical stress-strain (i.e. fault zones) and physic-chemical alteration. In this paper, the attempts made to understand the mechanical behavior of a gap-graded heterogeneous soil, named Highly Tectonized Phyllite (HTP), will be presented. To investigate this particular soil whose stress-strain response clearly depends on the grading, an experimental study was performed through triaxial tests mainly on reconstituted samples varying the composition of the mixture.