Evaluating the shear strength of a natural heterogeneous soil using reconstituted mixtures

Geotechnical characterisation of complex formations, transitional soils and heterogeneous materials requires specific care because their mechanical response is not straightforward. This is the case of a heterogeneous soil outcropping along a landslide-prone hillside where a dam shoulder had to be built. For a safe design of the dam it is necessary to pay specific attention to the slope stability, so a great effort has been devoted to the soil characterisation. The soil originated from a large tectonic strain deformation of the weak rock which produced a mélange of grain particles enclosed in fine grey matrix, geologically identified as Highly Tectonized Phyllite . The tectonic origin of the soil indicates that the variability in gradation of grains and fines content have to be taken into account to interpret and anticipate the pattern of the shear strength envelopes.