Penetration of cylindrical objects in soft mud

Abstract

The depth of penetration of objects impacting into soft sediments in the seafloor will depend on a number of factors including sediment shear strength, impact velocity, orientation of the object, and the density of the object. A critical step in developing a model for predicting depth of penetration is establishing a database of impact penetration measurements under closely controlled conditions. Toward this end, researchers at Texas A&M University constructed a 4-ft deep by 6-foot diameter test basin for conducting impact tests. The penetration experiments used medium to high plasticity sediments collected from the Gulf of Mexico seafloor. Sediments were processed to achieve uniformity and shear strength characteristics were measured using miniature vane tests. Impact tests were conducted using an apparatus that could vary the object density, impact velocity and orientation. Test results were evaluated based on a simplified model that used plasticity theory to describe instantaneous soil resistance and a simple kinetic model to describe motions of the object. The test results indicated that sediment shear resistance is a critical factor controlling penetration depths.