This article presents an experimental investigation on sand deformation above a group of two plate anchors using a digital image correlation (DIC) technique. The test setup developed for this study includes a test frame with loading and deformation measurement, a computer connected to a high-resolution camera and equipped with DIC software, and a test mold to host scale model anchor plates. A series of physical model tests were conducted under different configurations, including different embedment depths, anchor spacings, and sand densities. Based on the sand displacement fields obtained from DIC, it was found that anchor group efficiency occurs when there is an overlap in soil displacement fields. This overlap is influenced by the combination of embedment depth, sand density, and anchor spacing. There is a critical spacing that defines the spacing at which group anchors act individually. An empirical formula is proposed for the relationship between group efficiency and critical spacing for sand at different density conditions. The formula compares favorably with experimental results published in the literature.
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