Geochemical and engineering geological properties of the volcanic tuffs used in the Etruscan tombs of Norchia (Northern Latium, Italy) and a study of the factors responsible for their rapid surface and structural decay

The geochemical and engineering geological properties of the tuffs used in the rock-cut cliff tombs of the Etruscan necropolis of Norchia were investigated to evaluate their susceptibility to different weathering agents and confirm their origin. For the first time, materials were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analyses (TGA, DGA and DTG), scanning electron microscopy (SEM-EDS) and energy-dispersive X-ray fluorescence (ED-XRF), and their different origins confirmed. Tests of material properties indicate that both tuffs are poorly durable, but one of them is less susceptible to weathering. Although tombs made with the more resistant material show limited surface weathering, they undergo severe structural damage because of stress release and plant root infiltration. This, combined with the microclimatic conditions established inside river canyons, can trigger rock falls, leading ultimately to the complete destruction of these tombs.