Uplift Capacity of Strip and Circular Anchors in Soft Clay with an Overlay of Sand Layer

Abstract

Vertical uplift resistance of strip and circular horizontal plate anchors embedded in soft clay with an overlay of a sand layer has been computed by using plane strain and axisymmetric lower bound limit analysis in conjunction with finite elements and linear optimization. The improvement in the magnitude of the uplift resistance, with an overlay of the sand layer, has been expressed in terms of non-dimensional efficiency factors. It is found that the magnitude of the uplift resistance increases continuously with an increase in the thickness (H sand ) of sand layer up to a certain critical value of H sand /B; where B refers to either the width of strip anchor or the diameter of circular anchor. For c/(γB) = 1 and with ϕ = 40° for the overlying sand layer, the values of [H sand /B] cr become approximately equal to 3.1 and 1.6 corresponding to strip and circular anchor, respectively. For H sand /B > [H sand /B] cr , the analysis reveals that the anchor plate needs to be placed on the top of the clay stratum rather than embedding within the clay medium at a given depth (H). As compared to the circular anchor, the improvement in the uplift resistance with an overlay of sand layer becomes always more extensive for a strip anchor. The computational results have been obtained for different combinations of H/B, H sand/B and c/(γB). These results have been found to compare well with the different available theoretical and experimental data reported from literature.