On the liquefaction induced pore water pressure ratio underneath existing buildings

The catastrophic effects of seismically induced liquefaction recently observed during the Kahramanmaraş sequence (Turkey, 2023) confirmed the need of effective tools for predicting the effects of soil liquefaction on the built environment, to be used at the design stage. The main factors governing the seismic response of buildings founded on liquefiable sandy deposits are nowadays recognised. It is clear that the prediction of the damages depends on the correct estimation of earthquake induced excess pore water pressures Δu within the soil deposit, which cause the loss of soil shear strength and stiffness during the seismic shaking. While in free field conditions there are many models developed in literature able to predict the pore pressure ratio build-up (r_u,ff) induced by cyclic loading, the correct prediction underneath the footing (r_u,st) is a rather complex topic, still deserving research insight. By processing published centrifuge tests data, the paper proposes a simple expression of β (= r_u,st/r_u,ff) as a function of some relevant factors affecting the stress state within the liquefiable soil during the seismic shaking, grouped in a single, dimensionless parameter (Ψ).