Physical Modeling by Froude Number Similarity Law: Experimental Apparatus for Tests With Offshore Structure Anchors Penetrated With Water Jet

The torpedo pile is a Brazilian technology widely employed for anchoring offshore structures. Studies indicate that the use of vertical water jets applied at the pile tip can increase penetration efficiency and reduce inclination during installation. Considering the high costs and logistical challenges of full-scale testing, investigations using reduced physical models become a viable alternative. This study presents the development and application of an experimental apparatus based on the Froude Number Similarity Law, designed to perform penetration and pullout tests on reduced-scale torpedo pile models without fins, at a 1:76 length scale. To validate the system, an initial series of tests was conducted in fine granular soil using jets with a diameter equivalent to 12.5% of the pile's outer diameter. The results confirmed the proper performance of the apparatus, successfully reproducing in laboratory conditions the penetration process assisted by water jetting. A significant increase in penetration was observed compared to the self-weight condition, even at low flow rates (0.5 L/min), with an asymptotic trend as flow rate and jet velocity increased. Despite the substantial rise in jet velocities due to the smaller jet diameter, penetration depths were similar to those reported in the literature, indicating that jetting efficiency is more closely related to flow rate than to jet velocity. Scale effects inherent to the system were also recognized, reinforcing the importance of future analyses based on dimensionless groups derived from the Vaschy–Buckingham Π theorem to enable the transposition of laboratory results to field conditions.