Modeling the Excess Porewater Pressure Buildup in Pyroclastic Soils Subjected to Cyclic Loading

Although significant strides have been made in understanding the liquefaction phenomena, the recurrence of catastrophic seismic events continues to underscore the need for critical research in this area. The aim of the paper is to develop a better predictive model for liquefaction that can correctly describe the process of undrained pore pressure buildup in the case of pyroclastic soil. For this purpose, an experimental program was performed through undrained cyclic triaxial tests on three different pyroclastic soils, i.e., Cervinara (Italy), Campi Flegrei (Italy), and Rangiriri (New Zealand). The analyses of the experimental results show the dependency of the mechanism of excess porewater pressures on the stress history, stress state, and stiffness of the investigated soils by using two key parameters, $\psi$ and $\lambda$, derived from the steady-state theory. A new simplified porewater pressure model whose parameters show a functional relationship with the state parameters has been proposed.