Influence of Geogrid Reinforcement on Pullout Response of Granular Pile-Anchors (GPAs) in Expansive Soils

Abstract

This paper presents the influence of geogrid reinforcement on uplift capacity of granular pile-anchor (GPA) in expansive clay beds. In granular pile-anchor foundation system, footing is connected to the anchor plate provided at the bottom of granular pile through an anchor rod so that the uplift force on the footing due to swelling of expansive clay is reduced. Prediction of uplift capacity is necessary in the design of granular pile-anchors. Uplift capacity of GPAs can be increased by reinforcing it with geogrid layers placed at different depths from the base. Geogrid reinforcement prevents granular material reorientation due to uplift stress concentration on the anchor plate, leading to failure. The pullout capacity increased with increasing number of geogrid layers, decreasing spacing between them, and with decreasing distance between anchor plate and bottom geogrid. Uplift capacity increased by 65.61 % when 4 geogrid layers were used at a spacing of 20 mm. Pullout resistance was maximum when the bottom geogrid was placed at 20 mm above the anchor plate.