ABSTRACT
Studies have been carried out since 1970 in different countries on a variety of volcanic rocks: e.g. in Spain (e.g. Uriel & Serrano 1973, Serrano et al. 2002, González de Vallejo et al. 2006, Serrano et al. 2007); in Italy (e.g. Aversa & Evangelista 1998, Tommasi & Ribacchi 1998, Cecconi & Viggiani 1998, Rotonda et al. 2002, Cecconi et al. 2010); in Japan (Adachi et al. 1981); or in New Zealand (Moon 1993). In those studies it was observed that some of the volcanic materials, mainly the low density ones, have a very similar and peculiar stress-strain behavior. At low pressures they behave like a rock, with high modulus of elasticity and low deformations, while at high pressures their structure is broken and their deformability greatly increased behaving then more like soils.
