A GLE-based model for seismic displacement analysis of slopes including strength degradation and geometry rearrangement Valeria Bandini a , Giovanni Biondi a,n , Ernesto Cascone a , Sebastiano Rampello b a University of Messina, Messina, Italy b University of Rome La Sapienza, Roma, Italy article info Article history: Received 3 August 2014 Received in revised form 16 January 2015 Accepted 18 January 2015 Keywords: Slope displacement analysis Earthquake-induced displacements Mass transfer Cyclic degradation Shaking table tests abstract Seismic performance of natural slopes, earth structures and solid-waste landfills can be evaluated through displacement-based methods in which permanent displacements induced by earthquake loading are assumed to progressively develop along the critical sliding surface as a result of transient activation of plastic mechanisms within the soil mass. For sliding mechanisms of general shape the earthquake-induced displacements should be computed using a model that provides a closer approx- imation of sliding surface. When large permanent displacement are induced by seismic actions, due to substantial shear strength reduction, and significant changes in ground surface occur, an improved estimate of permanent displacement can be obtained using a model which accounts for shear strength reduction and mass transfer between adjacent portions of the slope resulting from geometry changes of ground surface during the seismic event. In this paper, a GLE-based model is proposed for seismic displacement analysis of slopes that accounts for shear strength degradation and for geometry rearrangement. Model accuracy is validated against experimental results obtained from shaking table tests carried out on small scale model slopes. Comparison of computed and experimental results demonstrates the capability of the proposed approach in capturing the main features of the observed seismic response of the model slopes. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction During strong earthquakes soils develop significant deforma- tions that may affect the stability conditions of natural slopes and earth structures possibly causing failures and involving significant losses in terms of damages to environment, structures and lifelines. Seismic performance of these geotechnical systems can be eva- luated through different methods of analysis, ranging from simpli- fied procedures to rigorous numerical methods, thus requiring different levels of accuracy for appropriate problem formulation, modelling of mechanical soil behaviour and analysis procedures. Among the available approaches to evaluate the seismic stabi- lity of slopes, the displacement-based approach represents a good compromise between computational effort and results accuracy and has the advantage of providing a quantitative assessment of earthquake-induced displacement using a rather simple numerical procedure. Permanent slope displacements induced by earthquake loading can be evaluated using the sliding block analysis, first proposed by Newmark [1], which requires a three-step procedure. First, the critical acceleration, which brings the system to a limit equilibrium condition, and the associated failure mechanism are determined through the pseudo-static approach; then, the equation of motion of the system is derived; finally, for a given acceleration time history, the cumulative displacement of the potential sliding mass is computed by double integration of the equation of motion. It is worth noting that the displacement analysis is not capable of reproducing the whole deformation pattern of a slope or earth structure but only the displacements due to shear deformations. Volumetric deformation possibly leading to compression and bulging rather than sliding cannot be captured by a Newmark- type computation ([2]). Therefore, the computed permanent displacement should merely be considered as an index of the seismic performance of the slope and not as the actual expected displacement. In the original formulation of Newmark’s sliding block analysis, the effects of possible reduction of soil shear strength and in turn of critical acceleration induced by seismic actions, as well as the effect of changes in slope geometry during the earthquake, are not taken into account. In the attempt of improving Newmark’s approach, studies were carried out dealing with single-, two- or multi-block models or with modified conventional slice methods. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/soildyn Soil Dynamics and Earthquake Engineering http://dx.doi.org/10.1016/j.soildyn.2015.01.010 0267-7261/& 2015 Elsevier Ltd. All rights reserved. n Correspondence to: Dipartimento di Ingegneria Civile, Informatica, Edile, Ambientale e Matematica Applicata, Contrada di Dio, S. Agata, Messina 98166, Italy. Tel.: þ39 90 397 7169; fax: þ39 90 397 7480. E-mail address: gbiondi@unime.it (G. Biondi). Soil Dynamics and Earthquake Engineering 71 (2015) 128–142