Role of numerical model and parameter variability on seismic response of slopes: the case of Las Colinas landslide

This paper presents the results of a sensitivity analysis on the influence of the strength, stiffness and damping parameters of the soil on the seismic response of a real slope. The analyses have been performed for the Las Colinas slope (El Salvador) using the finite element code PLAXIS and the data available in the literature. Las Colinas landslide was a destructive event which was triggered by the El Salvador earthquake on 13 January 2001. During this event, 183˙500 m3 of volcanic deposit slid and struck the houses on the foothill, killing 500 people. In this study a sensitivity analysis was performed to highlight the influence of the parameter uncertainties on the seismic response of the slope. The sensitivity analyses on the stiffness and strength parameters of the soil were performed by using their low, best and high estimates, using reported data and empirical equations. The sensitivity studies on the damping factor showed an unexpectedly large influence on the results. For a better understanding of this issue, the role of damping in each layer on the total response was examined separately. In addition, the effects of mesh and model sizes, as well as performance of different boundary conditions were investigated. The results show that, while a suitable numerical tool is in general capable of predicting and simulating the seismic response and failure of a complex slope, it is essential to undertake a careful evaluation of the mechanical parameters and modelling features. The results also show that for a realistic assessment of the uncertainties of the response it is important to identify the parameters that have the largest influence on the total response.