Numerical Investigation of Uplift Failure Mode and Capacity Estimation for Deep Helical Anchors in Sand

Abstract

The uplift capacity of helical anchors is generally taken as the control condition for design in different applications, including transmission tower foundations and offshore structures. However, it is difficult to identify the failure surface for a deep helical anchor, which may result in an incorrect assessment of uplift capability. This research proposes a new unified method to estimate the uplift capacity of deep single-helix and multi-helix anchors based on the investigation of failure mechanisms. The deep failure mode was identified by FEM analysis using a modified Mohr–Coulomb model considering the strain softening of sand, along with the coupled Eulerian–Lagrangian technique. Thereby, a simplified rupture surface is proposed, and the equations estimating the uplift capacity are presented by the limit equilibrium method. Two important factors—the lateral earth pressure coefficient and the average internal friction angle included in the equations—are discussed and determined. The comparisons with centrifugal tests verify the reasonability of the proposed method.

Installation Disturbance of Helical Anchor in Dense Sand and the Effect on Uplift Capacity Based on Discrete Element Method

“…Extensive experiments [8,13,[21][22][23][24][25][26][27][28][29][30], numerical analyses [12,[31][32][33][34][35][36][37], and theoretical analyses [38][39][40] have been conducted on the load-bearing performance of helix anchors. Tsuha et al [28] performed centrifuge uplift loading tests on 12 different types of piles installed in two sands with different densities to examine the effect of the number of helices on the performance of helical anchors in sand.…”