Technical note Effect of footing shape and load eccentricity on behavior of geosynthetic reinforced sand bed Ehsan Badakhshan *, 1 , Ali Noorzad Geotechnical Engineering, Faculty of Civil, Water & Environmental Engineering, Shahid Beheshti University, Tehran, Iran article info Article history: Received 4 May 2015 Received in revised form 22 January 2016 Accepted 30 November 2016 Keywords: Geosynthetics Circular and square footings Bearing capacity Reinforced sand abstract This paper presents the results from a laboratory modeling tests and numerical studies carried out on circular and square footings assuming the same plan area that rests on geosynthetic reinforced sand bed. The effects of the depth of the first and second layers of reinforcement, number of reinforcement layers on bearing capacity of the footings in central and eccentral loadings are investigated. The results indi- cated that in unreinforced condition, the ultimate bearing capacity is almost equal for both of the footings; but with reinforcing and increasing the number of reinforcement layers the ultimate bearing capacity of circular footing increased in a higher rate compared to square footing in both central and eccentrial loadings. The beneficial effect of a geosynthetic inclusion is largely dependent on the shape of footings. Also, by increasing the number of reinforcement layers, the tilt of circular footing decreased more than square footing. The SR (settlement reduction) of the reinforced condition shows that settle- ment at ultimate bearing capacity is heavily dependent on load eccentricity and is not significantly different from that for the unreinforced one. Also, close match between the experimental and numerical load-settlement curves and trend lines shown that the modeling approach utilized in this study can be reasonably adapted for reinforced soil applications. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction For the last four decades in Civil Engineering, application of geosynthetics has been known as a common technique to increase the ultimate bearing capacity of soils and decrease the settlement of footings. Among the range of geosynthetics available in the market, geotextiles are the most preferred type of geosynthetic materials for reinforcing the foundation beds. Many researchers (Hughes and Withers, 1974; Binquet and Lee, 1975a, 1975b; Huang and Tatsuoka, 1988,1990; Adams and Colin, 1997; Alawaji, 2001; Ghosh et al., 2005; Kumar et al., 2007; Mosallanezhad et al., 2007; Tafreshi and Dawson, 2010; Ghazavi and Afshar, 2013; Pinho-Lopes et al., 2015) reported when reinforcements were placed at an optimum depth below a footing (strip, square, rect- angular foundations) the beneficial effect of reinforcement can observed. These studies were focused on the ratio of the first layer of reinforcement from the foundation base, u, the foundation size, B,(u/B); the ratio of the reinforcement width, b, to the foundation size (b/B); and the ratio of the total reinforced depth, h, to the foundation size (h/B) and critical ratios of them. In the field of soil reinforcing with geosynthetic layers (in sand or clay) for circular foundations in centrally loaded, there has not been a lot of researches as compared to other foundations in the literature. Sitharam and Sireesh (2004) conducted a number of laboratory model tests to determine the bearing capacity of an embedded circular footing supported by sand bed reinforced with multiple layers of geotextiles. The test results demonstrated that the ultimate bearing pressure increased with embedment depth ratio of the foundation. Also, Basudhar et al. (2007) carried out experimental and numerical analyses on behavior of circular foot- ings with different size resting on reinforced sand with geotextile and reported that with increase in number of reinforcement layers, the settlement value gradually decreased. Similarly, Boushehrian and Hataf (2003) found that for the circular footings on rein- forced sand the maximum bearing capacity occurs at different values of embedment depth ratio depending on the number of reinforcement layers. For ratios of u/D greater than one reinforce- ment layers had no significant effect on bearing capacity. They also reported that choosing a rigid reinforcement did not always improve the effect on bearing capacity. Yetimuglu et al., 1994 * Corresponding author. E-mail address: e_badakhshan@sbu.ac.ir (E. Badakhshan). 1 http://www.sbu.ac.ir. Contents lists available at ScienceDirect Geotextiles and Geomembranes journal homepage: www.elsevier.com/locate/geotexmem http://dx.doi.org/10.1016/j.geotexmem.2016.11.007 0266-1144/© 2016 Elsevier Ltd. All rights reserved. Geotextiles and Geomembranes 45 (2017) 58e67