Estimation of Uplift Capacity of Helical Anchors in Clays

Abstract

Currently, helical anchors are being extensively used in the construction of transmission tower foundations, pipelines, and braced excavations. To arrive at the uplift capacity of these anchors, it is necessary to assume certain type of failure surface and in a few cases, cylindrical failure surface has been suggested. However, in this type of formulations the effect of spacing of helical plates is to be given due consideration and in the present study, this aspect has been taken into account. Pullout tests are conducted on four type of model anchors fabricated with different number of helical plates and spacing ratios in soft marine clay. From the test results, it is found that continuous cylindrical failure surfaces are formed in the case of anchors with helical plates spaced at a spacing ratio of 1.5. But in the case of anchors with helical plates at higher spacing ratios, well‐defined cylindrical failure surfaces could not be observed and in these cases; empirical formulations are suggested to estimate the capacities. The suggested formulations are verified with the reported lab and field test results and are found to be in good agreement.