Tip embedment depth of dynamically installed torpedo anchor: An experimental approach

In deep waters, dynamically installed torpedo anchors are the simplest, most economical and less time-consuming modern anchoring technique. In this technique, the target tip embedment depth estimation is an essential task in the design stage. This tip embedment depth depends on factors like aspect ratio, fin ratio, anchor ballast weight, drop height, tip shape and undrained shear strength of the underlying sea floor. Amongst these, the configuration of the tip geometry shape adopted plays a significant role, but only limited experimental or numerical studies were performed on these. The existing theoretical models do not predict the influence of the various tip shapes, which is a prime factor in the soil separation process. Due to the change in the tip profile, the penetration process becomes complex, and the choice of parameters considered in the tip embedment depth prediction models becomes dubious. Thus, the objective of the present experimental program is to run a series of 1g drop tests of instrumented model anchors in various test beds with the different tip configurations (conical - 30°, 45° and 60°, elliptical, ogive and hemisphere). In the process, the tip embedment process of these different anchors is also examined. The present experimental results match reasonably well with the theoretical model, based on the force equilibrium, for 60° conical tip anchor models with standard bearing capacity factor, whereas discrepancy appears for other kinds of tip shapes. In order to resolve this discrepancy, a coefficient called tip performance factor is estimated based on the experimental study for other tip profiles to be adopted in field conditions. Additionally, the parametric study was also extended experimentally to study the anchor ballast weight effect, drop height effect, fin arrangement effect and undrained shear strength effect.