Response of anchor foundations in geogrid reinforced sand under combined loads

The use of geogrid reinforcement has proven to be an effective measure to improve the anchor uplift capacity. However, previous studies are limited to analyzing the axial pullout capacity of plate anchors. In comparison, the anchor foundations employed in field are compelled to resist both uplift and lateral forces. In most cases, the foundation's safety against lateral forces dictates the design criteria for tall structures. Therefore, improving the foundation's lateral load-bearing capacity is of utmost importance. This paper presents a three-dimensional numerical analysis of anchor foundations in geogrid-reinforced sand under uplift and lateral forces. The results highlight the benefits of geogrid reinforcement on the anchor's response to uplift and lateral loads. The geogrid reinforcement is modelled using cable elements capturing the actual apertures responsible for tensile force mobilization along the geogrid ribs. A significant reduction in the displacements of the anchor foundation is observed in geogrid-reinforced sand, both in horizontal and vertical directions, when combined loads are applied on the anchor. However, the maximum reduction is found in the case of vertical uplift forces for higher values of the applied load. The practical implication of this study is demonstrated using a performance-based design example of transmission tower foundations in geogrid-reinforced sand.