Research Paper The effect of backfill cohesion on seismic response of cantilever retaining walls using fully dynamic analysis Abdolreza Osouli a,⇑ , Siavash Zamiran b a Department of Civil Engineering, Southern Illinois University Edwardsville, 61 Circle Dr., Edwardsville, IL 62026-1800, USA b Department of Civil Engineering, Southern Illinois University Carbondale, 1263 Lincoln Dr., Carbondale, IL 62901, USA article info Article history: Received 3 February 2017 Received in revised form 31 March 2017 Accepted 15 April 2017 Keywords: Retaining wall Cohesive sandy backfill Seismic earth thrust Fully dynamic analysis abstract The analyses of retaining walls in California showed many backfills are coarse material with some cohe- sion. In this investigation, seismic response of cantilever retaining walls, backfilled with dirty sandy materials with up to 30 kPa cohesion, is evaluated using fully dynamic analysis. The numerical simulation procedure is first validated using reported centrifuge test results. The validated methodology is then used to investigate the effects of three earthquake ground motions including Kobe, Loma Prieta, and Chi-Chi on seismic response of retaining walls. In addition, the input peak ground acceleration values are varied to consider a wide range of earthquake acceleration intensity. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Current seismic design criteria for retaining wall structures sug- gested by different organizations are based on estimating seismic earth pressure of the wall using analytical solutions (e.g. [1,10]. Different guidelines including AASHTO and Caltrans consider pseudo-static analytical solutions to identify seismic earth pres- sure [1,10]. The first analytical attempt as a pseudo-static method to evaluate seismic earth pressure of retaining walls was suggested by Okabe [27] and the method was verified in retaining walls with unsaturated and cohesionless soil material by Mononobe and Mat- suo [22] using shake table test results. The method developed by these investigators is known as Mononobe-Okabe (MO) method and is still widely used to determine seismic earth pressure of retaining walls. MO procedure is an extension of Coulomb theory and is based on limit equilibrium method and assumes an occur- rence of a failure wedge in the backfill. MO method considers the earthquake acceleration is uniform in the backfill and is applied to the center of gravity of the failure wedge. There are also many studies that evaluated the total seismic earth thrust (P ae ) experimentally [2,3,6,25,28,33] and numerically [6,9,12,15,14,30,31,40,42]. Specifically, Seed and Whitman [33], hereafter abbreviated as S&W, conducted different centrifuge tests on retaining walls with cohesionless backfill materials and pro- vided a simple equation for determining P ae , which linearly corre- lates with horizontal earthquake peak ground acceleration (PGA). Their experimental-based estimation has been used in design guidelines for evaluating P ae , e.g., US Army Corps of Engineers [39]. It is worth mentioning that the earthquake acceleration intensities for the mentioned numerical and experimental studies were limited to PGA ground motions of 0.2g to 0.4 g. In most of these studies, the cohesion factor of backfills and hysteretic behav- ior of soil were also neglected. Guidelines by AASHTO and state Departments of Transporta- tions suggest the use of granular materials as backfill for retaining wall constructions as they provide better drainage capacity and have less sensitivity to swell or shrinkage problems [1,10,23]. However, according to field observations in several cases, backfill materials have a various amount of cohesion [18]. Kapuskar [18] conducted field observations of more than 100 retaining wall and abutment backfills used in 20 different bridge sites in the State of California. It was concluded that out of 20 bridge sites, 15 of them had sandy backfills with low plasticity fines that had cohe- sion up to 95 kPa. Seismic response of retaining walls considering backfill cohe- sion has been taken into account analytically [11,29,36,35,37]. Most of these approaches were developed based on an extension of MO method with consideration of backfill cohesion, wall adhe- sion, and tension cracks in cohesive backfill materials. The MO- based methods have restrictions to be used for backfills with dif- ferent soil layers and complex geometries. Therefore, analytical methods based on trial wedge procedure has been proposed for backfills with various layers of soil or complex geometries [5]. http://dx.doi.org/10.1016/j.compgeo.2017.04.007 0266-352X/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: aosouli@siue.edu (A. Osouli), zamiran@siu.edu (S. Zamiran). Computers and Geotechnics 89 (2017) 143–152 Contents lists available at ScienceDirect Computers and Geotechnics journal homepage: www.elsevier.com/locate/compgeo