Technical Note Evaluation of Prediction Methods for Lateral Deformation of GRS Walls and Abutments Mahsa Khosrojerdi, S.M.ASCE 1 ; Ming Xiao, M.ASCE 2 ; Tong Qiu, M.ASCE 3 ; and Jennifer Nicks, M.ASCE 4 Abstract: Geosynthetic reinforced soil (GRS) walls and abutments are increasingly used to support transportation infrastructure. A pressing question in their response is the amount of horizontal deflection expected under service loads. This paper presents an evaluation of six methods for predicting the lateral deformation of GRS walls and abutments, namely the FHWA, Geoservice, CTI, Jewell-Milligan, Wu, and Adams methods. Field and laboratory performances of 17 GRS walls and abutments are compared with the predicted results from the six methods. A statistical analysis is then used to evaluate the conservativeness, accuracy, and reliability of these methods in predicting the maximum lateral deformation of GRS walls. The Adams method is the most accurate method for predicting the maximum lateral deformation if the amount of vertical deformation is reasonably known. Among the Geoservice, Jewell-Milligan, and Wu methods, which have the ability to predict the lateral deformation of GRS walls at various elevations where reinforcements are located, the Wu method is the most accurate and reliable method for predicting the lateral deformation of GRS walls. DOI: 10.1061/(ASCE)GT.1943-5606.0001591. © 2016 American Society of Civil Engineers. Author keywords: Abutment; Geosynthetic reinforced soil; Lateral deformation; Prediction method; Wall. Introduction In the design, construction, and maintenance of transportation in- frastructure, demand is increasingly placed on reducing the cost, shortening the construction duration, and maintaining serviceabil- ity during its service life. Geosynthetic reinforced soil (GRS) abutments provide an economical solution to accelerated bridge construction that uses readily available materials and equipment and performs well (Adams et al. 2011a). Accordingly, GRS struc- tures have gained increasing popularity in the world. GRS consists of closely spaced layers of geosynthetic reinforce- ment and compacted granular fill material. The spacing of GRS reinforcement typically does not exceed 30 cm and is typically 20 cm (Adams et al. 2011a). Because GRS abutments support bridge structures, determining the amount of their horizontal and vertical deformations under service load is of great importance. Laboratory and field tests have been carried out to physically model the behavior of geosynthetically reinforced structures subjected to static loading. For example, Abu-Hejleh et al. (2000, 2002), Adams (1997), Adams et al. (2002), Ketchart and Wu (1997), Helwany (1993), and Helwany et al. (2001) performed field tests on geo- synthetically reinforced bridge abutments with block facing and demonstrated that these structures have excellent performance char- acteristics and high load-carrying capacity. Benigni et al. (1996), Bueno et al. (2005), and Benjamim et al. (2007) evaluated the field performance of geosynthetically reinforced walls with wrap-around facing at the end of the construction stage, including the deforma- tion of these walls and the strains in the reinforcement layers. The study of Benigni et al. (1996) showed that the top third of the wall moved almost rigidly forward under surcharge loading. Bueno et al. (2005) and Benjamim et al. (2007) concluded that the largest hori- zontal deformation and reinforcement strain under self-weight oc- curred toward the face of the structure, approximately at midheight of the wall. Bathurst et al. (2000, 2001) conducted laboratory model tests to evaluate the capacities and behaviors of geosyn- thetically reinforced walls and abutments under different loading conditions to identify possible sources of conservatism in current methods of analysis. The geosynthetically reinforced structures in the aforementioned studies had various reinforcement spacings from 15 to 60 cm. Basic design guidelines for GRS abutments are available that outline recommended soil type, gradation, and level of compaction of the backfill soils, along with the vertical spacing, strength, stiff- ness, and length of reinforcement layers (Adams et al. 2011b; Nicks et al. 2013). Although these design guidelines are reasonably well established, the prediction of GRS walls and abutment deformation under applied service loads requires further investigation. A real- istic estimation for deformations of GRS abutments is important because differential movements of bridge substructures can nega- tively affect the ride quality, deck drainage, and safety of the trav- eling public as well as the structural integrity and aesthetics of the bridge, which can lead to costly maintenance and repair measures (Modjeski and Masters 2015). Regardless of settlement uniformity, ensuring adequate clearance for bridge elevations is dependent on the total movement. Based on these reasons, the service limit state (SLS) often controls the design of shallow bridge foundations (AASHTO 2014; Samtani and Nowatzki 2006a, b). The SLS 1 Graduate Student, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802. E-mail: mahsa@ psu.edu 2 Associate Professor, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802 (corresponding author). E-mail: mxiao@engr.psu.edu 3 Associate Professor, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802. E-mail: tqiu@engr .psu.edu 4 Research Geotechnical Engineer, Turner Fairbank Highway Research Center, Federal Highway Administration, 6300 Georgetown Pike, McLean, VA 22101. E-mail: jennifer.nicks@dot.gov Note. This manuscript was submitted on January 1, 2016; approved on June 10, 2016; published online on August 10, 2016. Discussion period open until January 10, 2017; separate discussions must be submitted for individual papers. This technical note is part of the Journal of Geotech- nical and Geoenvironmental Engineering, © ASCE, ISSN 1090-0241. © ASCE 06016022-1 J. Geotech. Geoenviron. Eng. J. Geotech. Geoenviron. Eng., 06016022 Downloaded from ascelibrary.org by Pennsylvania State University on 08/15/16. Copyright ASCE. For personal use only; all rights reserved.