Résumé de la publication

Helical anchors are commonly used in Brazil for guyed transmission towers subjected to static and cyclic wind loads. In most cases, these anchors are installed in tropical residual soil, a micro-structured material in which the shear strength is provided by soil bonding. During installation of a helical anchor, as the helical plate moves downward into the ground, the soil penetrated is sheared and displaced. Consequently, in this type of soil, anchor installation affects the soil shear strength significantly associated with a bonded structure. However, the cyclic responses of helical anchors in this type of structured soils are rarely reported. To address this problem, tests were conducted in a Brazilian residual soil to investigate the monotonic, cyclic and post-cyclic performances of single-helix anchors. Field tests used two instrumented single-helix anchors installed in this typical residual soil of sandstone, which is frequently observed in large areas in the southern Brazil. The testing results indicate that the disturbance caused by the anchor installation affected the monotonic uplift performance markedly. The results of cyclic loading tests also show no significant degradation of helix bearing resistance and reduced displacement accumulation with increasing load cycles. This is perhaps due to the soil improvement caused by previous loading, which then increases the stiffness response of the anchor.