Pullout resistance of inclined anchors embedded in geogrid reinforced sand

Transmission tower foundations experience large vertical uplift forces during their lifetime. These forces can be resisted by providing anchor foundations below the tower. In this study, laboratory experiments were conducted to investigate the pullout capacity of inclined plate anchors in dry sand. The capacity of inclined anchor significantly improved in the presence of geogrid reinforcement on top of the anchor plate. Besides, the pullout capacity increased with the inclination angle (30 degrees, 45 degrees, 60 degrees) both in unreinforced and reinforced soil. It was observed that the ultimate pullout load is significantly influenced by the embedment depth of the anchor plate and relative density of the backfill material. The experimental results were compared with a three-dimensional numerical model developed in FLAC3D. The comparison shows good agreement between the experimental and numerical results, and the numerical model can predict the pullout behaviour of the inclined anchor plate both in unreinforced and reinforced soil. Comparison of uplift resistance of pile and anchor foundations are shown through a design example of a transmission tower foundation. Results indicate that inclined anchors embedded in reinforced soil can resist the uplift forces at shallow depth compared to piles.