Two-dimensional nonlinear dynamic analysis of a liquefaction case history considering spatial variability and long-duration megathrust earthquakes

Abstract

We analyzed the unusual liquefaction response of the Los Presidentes site in Concepci ‘ on, Chile, during the 2010 Mw 8.8 Maule earthquake, using a series of twodimensional nonlinear dynamic analyses (NDAs) on a well characterized subsurface. This site, characterized by interbedded clean and silty sands followed by a dense sand unit, included four identical towers that experienced different settlements, with maximum values reaching 40 cm for the most damaged tower to zero for the less affected one. We used SPT, CPTu, and Vs tests to characterize the soil’s spatial variability. The NDAs used the PM4Sand and PM4Silt soil constitutive models implemented in OpenSees. The results suggest that the shear-induced deformation mechanism controls the dynamic response. The computed settlements matched post-earthquake LiDAR and field measurements, while liquefaction vulnerability indexes underestimated observed manifestations. Our results show that liquefactioninduced settlements due to megathrust earthquakes greatly differ from those induced by crustal ground motions.