Liquefaction of Volcanic Soils: Undrained Behavior under Monotonic and Cyclic Loading

AbstractVolcanic pyroclastic deposits generally have a metastable and collapsible structure, which may lead to their liquefaction under monotonic, cyclic, and dynamic loading. Their structure could be partly attributed to the nature of the pyroclastic particles, especially their lightweight, fragile and porous features. In comparing the results of monotonic and cyclic undrained triaxial tests performed on Cervinara soil, the steady-state concept is used to define the occurrence of liquefaction. A significant part of the experimental program on Rangiriri soil is carried out to highlight the role of the fragility of pyroclastic particles on the occurrence of liquefaction. The comparison between the results obtained on the two types of pyroclastic soils shows the possibility of explaining the undrained mechanism of pore pressure buildup using the state parameter ψ. The parameter ψ seems to be useful also in comparing the results obtained on pyroclastic soils with those on ordinary sands. The state parameter has a clear physical significance that could be used to define a more reliable model of undrained pore pressure buildup for soils of different natures.