Contents lists available at ScienceDirect Geotextiles and Geomembranes journal homepage: www.elsevier.com/locate/geotexmem Upper bound seismic limit analysis of geosynthetic-reinforced unsaturated soil walls H. Alhajj Chehade a,b , D. Dias c,d,* , M. Sadek b , O. Jenck a , F. Hage Chehade b a Univ. Grenoble Alpes, CNRS, Grenoble INP**, 3SR, 38000, Grenoble, France b Lebanese University, Doctoral School of Sciences and Technologies, Beirut, Lebanon c Hefei University of Technology, School of Automotive and Transportation Engineering, Hefei, China d Antea Group, Antony, France ARTICLE INFO Keywords: Geosynthetics Unsaturated soil Earth retaining wall Limit analysis Pseudo-dynamic Discretization ABSTRACT The assessment of the internal stability of geosynthetic-reinforced earth retaining walls has historically been investigated in previous studies assuming dry backfills. However, the majority of the failures of these structures are caused by the water presence. The studies including the water presence in the backfill are scarce and often consider saturated backfills. In reality, most soils are unsaturated in nature and the matric suction plays an important role in the wall's stability. This paper investigates the internal seismic stability of geosynthetic-re- inforced unsaturated earth retaining walls. The groundwater level can be located at any reinforced backfill depth. Several nonlinear equations relating the unsaturated soil shear strength to the matric suction and different backfill type of soils are considered in this study. The log-spiral failure mechanism generated by the point-to- point method is considered. The upper-bound theorem of the limit analysis is used to evaluate the strength required to maintain the reinforced soil walls stability and the seismic loading are represented by the pseudo- dynamic approach. A parametric study showed that the required reinforcement strength is influenced by several parameters such as the soil friction angle, the horizontal seismic coefficient, the water table level, the matric suction distribution as well as the soil types and the unsaturated soils shear strength. 1. Introduction Geosynthetic-reinforced soil retaining walls are composite materials formed by a compacted backfill and geosynthetic reinforcement ele- ments (Geosynthetic straps, geogrids or geotextiles). These structures introduced in the 1970s (Yu et al., 2016) are now a mature technology used worldwide due to their economic advantages and successful per- formance during strong earthquakes (Masini et al., 2015; Latha and Santhanakumar, 2015; Gaudio et al., 2018a). The methods used for the seismic analysis of reinforced earth walls can be classified into four major categories: limit equilibrium methods (Leshchinsky et al., 2009; Pain et al., 2017), limit analysis methods (Michalowski, 1998; Abd and Utili, 2017a, 2017b; Alhajj Chehade et al., 2019a; Alhajj Chehade et al., 2019c), experimental methods (Huang, 2013; Wang et al., 2015) and numerical approaches (Ling et al., 2010; Gaudio et al., 2018a). Among these methods, the limit equilibrium is the most commonly used tech- nique due to its simplicity. However, by using this method, it is ne- cessary to assume a number of assumptions regarding the forces between the slices and the stresses distribution along the failure surface. Hence, these method's results cannot be considered as rigorous. A solution obtained from the limit equilibrium method is not ne- cessarily a lower or upper bound which is the case when the limit analysis method is adopted. The latter is an effective alternative ap- proach to deal with the stability problems of geotechnical structures, considering the stress-strain relationship neglected by the former (Chen et al., 1969). It is based on the balance of the rates of external work and the internal energy dissipated. In last two decades, this approach was adopted by many researchers to investigate the seismic internal stabi- lity of reinforced soil retaining walls. Michalowski [1998] and Ausilio et al., [2000] used the kinematic theorem of limit analysis to determine the required reinforcement strength for structures stability. He et al., [2012] used the same approach to calculate the critical seismic yield acceleration coefficient and the permanent displacement of soil-nailed slopes. Abd and Utili (2017b) investigated the seismic internal stability of reinforced soil slopes with consideration of the cracks. Gaudio et al., [2018b] developed a seismic design approach for geosynthetic- https://doi.org/10.1016/j.geotexmem.2020.02.001 * Corresponding author. Hefei University of Technology, School of Automotive and Transportation Engineering, Hefei, China. E-mail addresses: hicham.alhajjchehade@3sr-grenoble.fr (H. Alhajj Chehade), daniel.dias@anteagroup.com (D. Dias), marwan.sadek@ul.edu.lb (M. Sadek), orianne.jenck@3sr-grenoble.fr (O. Jenck), fchehade@ul.edu.lb (F. Hage Chehade). Geotextiles and Geomembranes xxx (xxxx) xxx–xxx 0266-1144/ © 2020 Published by Elsevier Ltd. Please cite this article as: H. Alhajj Chehade, et al., Geotextiles and Geomembranes, https://doi.org/10.1016/j.geotexmem.2020.02.001