Abstract: Based on the mesh regeneration and stress recovery of modified REP technique, a three dimensional large deformation finite element (FE) approach is presented to study the interaction between the cohesive soil and square plate anchors subjected to the pulling-up force. Different from traditional small-strain FE methods, large deformation analyses can simulate anchors’ pulling out process completely. If the soil beneath the anchor is always attached to the anchor base, the uplift capacities of square anchors are found to be very close to that of circular anchors. Once an anchor in the weightless soil is pulled up, the anchor base separates with soil immediately. In such case, large deformation analyses show the breakout capacity factor of square anchors is slightly lower than circular anchors. The breakout factors from large deformation analyses agree well with model test data. Both the small strain FE and lower bound theorem neglect the effect of anchor’s large displacement on the uplift resistance, tending to overestimate the capacity of deep anchors. A simplified method is developed to estimate the uplift capacity of square anchors for industrial applications.

Key words: large deformation, offshore foundation, plate anchor, finite elements, bearing capacity