Shape effects on penetration of dynamically installed anchors in a transparent marine clay surrogate

The effect of shape on the penetration of low-speed penetrators, traveling under 10 m/s, such as dynamically installed anchors, gravity-fall penetrometers, projectiles, and unexploded ordnances, is explored. A transparent surrogate was used to simulate the behavior of a soft marine clay to permit visualizing anchor deceleration. Thirteen 19-mm diameter anchors were employed. Geometric parameters included fin shape and longitudinal grooves. Measurements of penetrator deceleration, from which the soil penetration resistance was computed, were further resolved into force on the nose, fins, and frictional forces. For this material, the ratio of nose-bearing stress to the undrained shear strength was about 8.2 and 4.5 for the nose and fins, respectively, and the effective friction coefficient was 0.3. The study demonstrates the effect of various geometric properties of an anchor on its deceleration and depth of burial. Finally, penetration depth was related to the soil and anchor properties using an equation that was also successful in predicting the depth of burial of several published case histories within 10% of the reported values.