Sand Deformation around an Uplift Plate Anchor Jinyuan Liu, P.E., P.Eng., M.ASCE 1 ; Mingliang Liu 2 ; and Zhende Zhu 3 Abstract: This paper presents an experimental investigation on soil deformation around uplift plate anchors in sand by using digital image cor- relation (DIC). The experimental setup consists of a camera, loading frame, plexiglass mold, and computer, which is developed to capture soil deformation during anchor uplifting. A series of model tests are performed to investigate the influence of particle size, soil density, and anchor embedment depth on soil deformation. A set of images captured during anchor uplifting are used to calculate soil displacement fields by DIC. The failure surface is studied by tracking the points with maximum shear strain values. On the basis of this study, it is found that soil deformation and the pullout resistance of plate anchors are substantially influenced by soil density and anchor embedment depth, whereas particle size within the studied range has limited influence. In dense sand, the shape of the failure surface changes from a truncated cone above a shallow anchor to a combined shape of a curved cone and a truncated cone for a deep anchor. In contrast, in loose sand a cone-shaped failure surface is formed within the soil mass above a shallow anchor; however, no failure surface is observed for a deep anchor, where the compressibility of soil is the dominating factor that influences the behavior of deep plate anchors in loose sand. DOI: 10.1061/(ASCE)GT.1943-5606.0000633. © 2012 American Society of Civil Engineers. CE Database subject headings: Anchors; Pullout; Failure modes; Sand (soil type); Soil deformation. Author keywords: Anchor; Pullout capacity; Scaled model; Digital image correlation; Particle image velocimetry; Failure mode. Introduction Plate anchors have been widely used as an efficient and reliable anchorage system to resist uplift forces that act on structures, such as transmission towers, offshore floating platforms, submerged pipelines, and tunnels. The extensive use of plate anchors has motivated researchers to achieve a more thorough understanding of anchor behavior for more than half a century. The pullout capac- ity of soil anchors relies on many factors, such as anchor geometry, embedded depth, and local soil conditions. Many methods of test- ing have been used to study the behavior of anchors, including field tests, laboratory tests, numerical analyses, and analytical solutions. Large-scale field tests on foundations for transmission towers and shafts contributed to the development of early empirical design methods (Giffels et al. 1960; Ireland 1963; Tucker 1987; Sutherland 1988). More recent design methods have been develo- ped on the basis of scaled model tests or numerical investigations. Small-scale model tests have been performed to understand anchor failure modes for different anchor geometries under various soil conditions (Balla 1961; Vesic 1971; Ilamparuthi et al. 2002). Numerical methods, including the finite-element method (FEM), also have been used to study plate anchors in both sand and clay. For example, Rowe and Davis (1982) used FEM to analyze a strip anchor in sand and found that dilatancy significantly influences the ultimate pullout resistance. Sakai and Tanaka (2007) performed an FEM analysis of shear band development for a circular anchor in sand. Analytical solutions were also developed to calculate the pull- out capacity of plate anchors in sand on the basis of an equilibrium approach on an assumed failure plane (Baker and Kondner 1966; Meyerhof and Adams 1968; Murray and Geddes 1987). Among various failure surfaces, there are primarily three dis- tinctive failure modes proposed by several researchers, as shown in Fig. 1. The first type of failure surface is a frictional cylinder me- thod that was first proposed by Majer (1955), as shown in Fig. 1(a). The pullout capacity is computed from the weight of the soil within the cylindrical failure surface directly above the anchor plus the frictional resistance along this surface. Because the failure mass mobilized by an anchor is normally larger than the cylinder above the anchor, the pullout capacity tends to be underestimated on the basis of this type of failure surface (Ilamparuthy et al. 2002). The second type of failure surface was first proposed by Mors (1959), which is a truncated cone that extends from the anchor with an apex angle of 90° þ ϕ, where ϕ is the friction angle of soil, as shown in Fig. 1(b). The pullout capacity is calculated to be only the weight of the soil on the truncated cone. The Mors method is usually too conservative for shallow anchors because it ignores the frictional force along the failure surface. However, it overestimates the pull- out capacity for deep anchors where the failure surface normally does not extend to the ground surface and will be smaller than the assumed truncated cone. The third type of failure surface is a circular failure surface that extends from the edge of the anchor and intersects with the ground surface at an angle of approximately 45° À ϕ∕2, as shown in Fig. 1(c). This type of failure surface was observed by Balla (1961) and Baker and Kondner (1966). Although extensive research has been performed to understand anchor behavior, discrepancies continue to vary extensively be- tween model prediction and actual measurement. It is believed that these discrepancies are attributable to a lack of full understanding of both anchor behavior and its interaction with the surrounding soil during anchor uplifting. Most of the previous experiments have only focused on the measurement of the final shape of the failure surface because of limitations of testing equipment and methods. This paper presents an experimental investigation of soil defor- mation around an uplift anchor plate in sand by using digital image 1 Associate Professor, Dept. of Civil Engineering, Ryerson Univ., Toronto, Canada (corresponding author). E-mail: jinyuan.liu@ryerson.ca 2 Project Engineer, Henan Electric Power Survey and Design Institute, Zhengzhou, China. E-mail: mingliang.liu79@gmail.com 3 Professor, Geotechnical Research Institute, Hohai Univ., Nanjing, China. E-mail: zzdnj@hhu.edu.cn Note. This manuscript was submitted on September 24, 2009; approved on September 7, 2011; published online on September 9, 2011. Discussion period open until November 1, 2012; separate discussions must be sub- mitted for individual papers. This paper is part of the Journal of Geotech- nical and Geoenvironmental Engineering, Vol. 138, No. 6, June 1, 2012. ©ASCE, ISSN 1090-0241/2012/6-728–737/$25.00. 728 / JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING © ASCE / JUNE 2012 Downloaded 07 Jun 2012 to 141.117.16.76. Redistribution subject to ASCE license or copyright. Visit http://www.ascelibrary.org