Axial interaction between anchor chain and sand. Part I: Monotonic loading test

Abstract

For the mooring line embedded in seabed, the axial soil resistance directly affects the tension transfer characteristic along the mooring line. Effective width parameter Et was commonly adopted to assess the axial resistance of anchor chain. However, neither the chain axial resistance nor its effective width parameter in sand has been fully understood. In this two-part paper, a series of axial loading tests between chain and sand were conducted. Part I shows the monotonic loading results, and Part II aims to study the cyclic loading behavior. In Part I, a kind of novel chain-soil interaction apparatus was first developed, and the method for acquiring the axial resistance was proposed. On this basis, the influences of confining stress, chain nominal diameter, sand particle size and relative density were investigated in detail. It is found that when the chain axial resistance is fully mobilized, the effective width parameter in sand ranges from 8.91 to 11.94. The statistical average value Et=10.34 is quite close to the normalized chain perimeter Pc=10.37(3.3π). Then, an example was given to show how to calculate the chain profiles in sand using the proposed Et expression. A method for calculating the chain profile in sands was verified by the centrifuge test results. The calculation results show that higher Et values lead to larger force inclined angles at the padeye. Under the condition, the anchor will suffer larger vertical loads due to the increase of the inclination angle.