Cyclic and post-cyclic monotonic response of a single-helix anchor in sand

In recent years, the use of helical anchors for guyed transmission towers has increased considerably in Brazil. This type of structure is subjected to important environmental cyclic loadings, but their effects are typically ignored in the design process. Under this scenario, this paper presents the preliminary experimental results of an investigation of the cyclic and post-cyclic monotonic responses of a single-helix anchor in very dense sand. Three different combinations of high-level loading cycles, simulating the effects of high wind speeds on the anchors of the guyed towers, were evaluated using centrifuge tests on an instrumented model anchor. The results indicate that although a rapid degradation of shaft resistance was observed in all tests, the soil loosened by the anchor installation was densified due to the cyclic loading improving the monotonic post-cyclic response.