Experimental Study on Tensile Bearing Capacity of Single and Group Helical Anchors

This paper investigates the tensile bearing capacity of both single and group helical anchors through small-scale physical modeling. The study evaluates anchor performance and group efficiency at varying spacings, depths, and helix diameters in medium-dense and dense wet sands. Results indicate that increasing helix diameter improves the tensile capacity of single anchors. However, the efficiency improvements associated with larger helix diameters are more pronounced in medium-dense sand. The failure mechanism for single anchors differs depending on soil density, with local failure observed in dense sand. Optimal spacing for anchor groups was determined to be 7Db in medium-dense sand and 9Db in dense sand, where Db refers to the helix diameter. While anchors in dense sand exhibited higher tensile capacity, their efficiency was lower compared to those in medium-dense sand, ranging from 0.36 to 0.85 in medium-dense sand and 0.54 to 0.76 in dense sand. Maximum efficiency occurred at 7 to 9 times the helix diameter. Furthermore, group anchors demonstrated less upward displacement than single anchors, and increased embedment depth enhanced tensile capacity. The tensile capacity of helical anchor groups was found to increase with larger helix diameters when placed at optimal spacing.