Undrained cyclic loading of pyroclastic soils: a new pore water pressure build-up model

Earthquake-induced excess pore water pressure in saturated granular soils has been studied for many years, but it is still an important area of research, as demonstrated by the most recent seismic events that caused devasting liquefaction-induced damage, e.g., in Türkiye 2023, Italy 2012, and New Zealand 2010-2011. The mechanism of undrained pore pressure build-up in pyroclastic soil under cyclic loading is analyzed within the framework of the steady state theory through cyclic triaxial tests performed on different pyroclastic soils (i.e., Cervinara (Italy) and Rangiriri (New Zealand)). The analyses of the experimental results show the dependency of the mechanism of excess pore water pressures on the history and stress state of the investigated soil by using two key parameters of the steady state theory. A new pore water pressure model based on these two key state parameters is proposed to reproduce the response of granular soils, which can be of a different nature from the pyroclastic ones.