A dynamic penetrometer for rapid assessment of seafloor parameters

Information on geoacoustic and geotechnical parameters of the seafloor is important in sonar performance evaluation as well as in engineering applications. Since measurement of these parameters using traditional methods usually involves some rather elaborate experimental procedures, there is the need for a simple system that can remotely measure some of these parameters from a moving ship or aircraft. To accomplish this a new technique using a probe similar to the expendable bathythermograph (XBT) has been developed wherein the thermistor used to measure water temperature is replaced by an accelerometer. When the probe first impacts the bottom there is rapid deceleration controlled by the shear strength of the sediment, followed by a period of damped oscillation with frequency dependent on the geoacoustic properties of the sediment. Thus when the impact signature is fully analyzed it is possible to obtain information on both the shearing strength of the bottom as well as the geoacoustic properties. At pre...