Upgrades to the Acoustic Coring System
Abstract
Sediment cores provide valuable insight on the physical properties of the seabed, and laboratory measurements of sediment wave speed from cores are often considered ~ground truth~. However, sound-speed estimates obtained from cores can be inaccurate due to changes in pressure, temperature, and mechanical properties of the sediment caused by removal of the core from the seabed and its subsequent transport to the laboratory. To address these issues, a system for obtaining in situ measurements of geoacoustic properties has been developed at the Applied Research Laboratories at the University of Texas at Austin. Compressional and shear wave speed and attenuation are estimated from signals transmitted across the diameter of the core barrel as the corer penetrates the seabed. The transducers are mounted outside the nose cone to minimize the effect of sediment disturbance caused by penetration of the corer. Compressional wave measurements are obtained with rod-mounted piezoelectric cylinders, and shear wave measurements are obtained with bender elements mounted in flat blades. Compressional andshear wave speed and attenuation are estimated from differential measurements made with two receivers. An engineering test of the system was conducted in the New England Mud Patch in April 2016, and successful measurements were made of the compressional wave speed profile as a function of depth within the seabed. These measurements demonstrate the potential of this system for wide use in ONR experiments. Funds are requested for system upgrades that will enable the system to obtain measurements to greater depths within the seabed as well as to increase measurement resolution.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 03, 2017
- Source ID
- N000141712193
Entities
People
- Megan S. Ballard
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Austin