A robust empirical model to estimate earthquake-induced excess pore water pressure in saturated and non-saturated soils

In engineering practice, the liquefaction potential of a sandy soil is usually evaluated with asemi-empirical, stress-based approach computing a factor of safety in free feld conditions,defned as the ratio between the liquefaction resistance (capacity) and the seismic demand.By so doing, an estimate of liquefaction potential is obtained, but nothing is known on thepore pressure increments (often expressed in the form of normalized pore pressure ratioru) generated by the seismic action when the safety factor is higher than 1. Even thoughru can be estimated using complex numerical analyses, it would be extremely useful tohave a simplifed procedure to estimate them consistent with the stress-based approachadopted to check the safety conditions. This paper proposes such a procedure with reference to both saturated and unsaturated soils, considering the latter as soils for which partial saturation has been artifcially generated with some ground improvement technologyto increase cyclic strength and thus tackle liquefaction risk. A simple relationship betweenthe liquefaction free feld safety factor FS, and ru(Sr) is introduced, that generalizes a previous expression proposed by Chiaradonna and Flora (Geotech Lett, 2020. https://doi.org/10.1680/jgele.19.00032) for saturated soils. The new procedure has been successfullyverifed against some experimental data, coming from laboratory constant amplitude cyclictests and from centrifuge tests with irregular acceleration time histories for soils having different gradings and densities.