Performance of dynamically installed anchors subjected to vertical and inclined cyclic loading in clay: experimental investigation

Anchors employed in offshore floating systems may experience “cyclic fatigue” due to strain-softening of the seabed soil under long-term cyclic loading. The reconsolidation of the soil during the cyclic loading process however will potentially improve the anchor stability over the entire life cycle. In this study, a series of laboratory model tests with ultra-high cycle numbers (∼10 6 ) were conducted to investigate the impact on the stability of a newly developed multi-line anchor of cyclic loading levels, uplift angles, and anchor types. Test results find that the critical uplift loading avoiding the “cyclic-induced fatigue failure” of the anchor is ∼0.6 F u, m ( F u, m is the ultimate monotonic uplift capacity) under vertical loading and is ∼0.7 F u, m for the anchor under 45° inclined loading. The post-cyclic monotonic uplift capacity exhibits an increase of 10%–70% compared with that in the monotonic uplift test, indicating the reconsolidated effect of the soil is beneficial for improving the anchor stability. Multi-amplitude cyclic tests find that previous loading procedures with relatively small-amplitude loading levels can restrain the accumulation of the uplift displacement during the subsequent loading procedure with relatively high-amplitude loading levels.