A Penetrometer for Deep Ocean Seafloor Exploration

This paper describes an expendable dynamic penetrometer for measuring seafloor penetrability and undrained shear strength at water depths to 6,000 meters. The components of the penetrometer are described, procedures for its use are given, and a method for determining the soil strength from the penetrometer data is presented. The results of some of the 50 penetrometer tests in seafloor soils that include sands, clays, and oozes are presented. Shear strength results derived from the penetrometer data are compared to other in-situ or laboratory shear strength data. It is concluded that the Doppler penetrometer system is reliable, simple to use, and that reasonable estimates of undrained shear strength profiles can be obtained.