A robust empirical model to estimate earthquake-induced excess pore water pressure in saturated and non-saturated soils
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A robust empirical model to estimate earthquake‑induced excess pore water pressure in saturated and non‑saturated soils Lucia Mele1 · Anna Chiaradonna2 · Stefania Lirer3 · Alessandro Flora1 Received: 22 July 2020 / Accepted: 28 September 2020 © Springer Nature B.V. 2020
Abstract In engineering practice, the liquefaction potential of a sandy soil is usually evaluated with a semi-empirical, stress-based approach computing a factor of safety in free field conditions, defined 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 the pore pressure increments (often expressed in the form of normalized pore pressure ratio ru) generated by the seismic action when the safety factor is higher than 1. Even though ru can be estimated using complex numerical analyses, it would be extremely useful to have a simplified procedure to estimate them consistent with the stress-based approach adopted 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 artificially generated with some ground improvement technology to increase cyclic strength and thus tackle liquefaction risk. A simple relationship between the liquefaction free field 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 successfully verified against some experimental data, coming from laboratory constant amplitude cyclic tests and from centrifuge tests with irregular acceleration time histories for soils having different gradings and densities. Keywords Liquefaction · Excess pore pressure generation · Factor safety · Non-saturated soils
1 Introduction Earthquake induced liquefaction is a phenomenon strongly linked to pore water pressure build-up within cohesionless soil layers during the seismic action. The simultaneous generation, dissipation, and redistribution of excess pore pressures within the layers of a soil deposit can significantly modify the seismic response of the whole deposit. * Lucia Mele [email protected] Extended author information available on the last page of the article
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Bulletin of Earthquake Engineering
Several relationships have been proposed in literature to predict the pore pressure build-up induced by cyclic loadings, traditionally divided in three groups: stress-based (Lee and Albaisa 1974; Seed et al. 1975b; Booker et al. 1976; Chameau and Clough 1983; Wang and Kavazanjian 1989; Liyanapathirana and Poulos 2002; Polito et al. 2008; Cetin and Bilge 2012), strain-based (Martin et al. 1975; Dobry et al. 1985) and energy-based models (Green et al. 2000; Baziar et al. 2011). The first to be developed were the stress-based models that were calibrated on the results of cyclic stress-con
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