Model Anchor Tests in Cohesionless Soil

Tandem (piggyback) and parallel anchor rigging arrangements have been found that result in anchor system capacities that exceed twice the capacity of a single anchor. These tests are part of a program to determine effective methods of utilizing high efficiency anchors in multiples to satisfy expanding fleet mooring requirements. Scale models of a Navy STATO anchor were tested in multiple arrangements in a sand test bed. Anchor arrangements have been found that increase anchor system capacity by 25% over twice the single anchor capacity without decreasing anchor stability. The typical fleet mooring arrangement of side‐by‐side parallel anchors decreases the anchor system capacity to less than twice the single anchor capacity due to anchor interference. Staggering the anchors by at least an anchor length increased the anchor system capacity to more than twice the single anchor capacity. Dragging the anchors far enough for the rear anchor to penetrate the soil disturbed by the forward anchor can result in a total anchor capacity exceeding twice the single anchor capacity in sand.