Tangential Shear Behavior between Sand and Anchor Chain-Paper

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The study examines tangential shear between anchor chains and sand, an interaction that affects mooring-line tension transfer when chains lie on or are embedded in the seabed. Because existing guidance and research largely concern clay, the authors conducted laboratory tests to characterize chain–sand resistance and estimate the effective chain width for engineering use.<br /><br />Twenty-eight tests produced 14 usable test groups. Experiments used studless chains with nominal diameters of 6, 8, and 10 mm and dry Pingtan sand in two particle-size ranges. The researchers varied shear speed, confining stress, chain diameter, and sand particle size, and calculated tangential resistance after accounting for rod friction and chain-tip resistance.<br /><br />Resistance generally followed a bi-linear pattern: it rose approximately linearly with displacement, then approached a stable value. Changing shear speed from 0.001 to 5 mm/s had negligible effect. Higher confining stress increased resistance and generally required more displacement to mobilize it fully. Larger chain diameters also increased resistance, while effective width varied little with diameter. Fine sand showed more pronounced hardening and required greater displacement than coarse sand, although the stable effective-width values were similar.<br /><br />For the tested conditions, tangential resistance was generally mobilized within about one nominal chain diameter of displacement, and the effective-width parameter ranged from 8.91 to 11.94. These findings provide parameters for mooring-system analysis and engineering design. The authors recommend further testing, particularly to investigate cyclic chain–sand resistance.

Keywords

anchor chains

sand interaction

tangential shear

mooring-line tension

chain–sand resistance

seabed embedment

effective chain width

laboratory tests

confining stress

engineering design