Unsaturated sand in the stability of the cuesta of the Temple of Hera (Agrigento)

In the Valle dei Templi in Agrigento seven Doric temples stand lengthwise the crest of a rigid calcarenite cuestaover a layer of carbonate sand which lies along a thick stratum of clays. The environment is highly prone to landslides since topplingsof calcarenite blocks often occur. The rock slopes are moving back and the slope edge draw near to the foundation of theTemple of Hera Lacinia contributing to increase their perilous condition. To assess the role of unsaturated sands in the instabilityprocesses, after the compositional and textural analysis of the material, direct shear tests and oedometer tests have been carried outon sand samples initially at the natural state, with low or very low values of natural water content, and finally at full saturation.The mechanical behaviour of sands seems one of the main causes of the instability influenced by the presence of an open metastablestructure, which develops through bonding mechanisms generated via suctions and/or through cementing material such as clayor salts.