Acoustical properties of mud sediments
Abstract
The proposed project continues previous work with the development of a theoretical framework for explaining the acoustical e ects of the varied nature and underlying physics of the various types of mud layers that are found in marine sediments. The theory is expected to include the electrochemical nature of the clay particles that are an invariable constituent of mud, the forces(such as van der Waals forces) that a ect the inter-positioning of clay particles, the forces on the silt particles in the mud, and the positioning of the silt particles. The envisioned work will also identify and quantity the fundamental principles and the principal mechanisms that govern the propagation of compressional and shear waves in mud. In particular, this work will lead to the improved prediction of compressional and shear wave velocities, given limited informationconcerning the composition of the mud and its morphology. A theory will be developed that identi es and quanti es the principal mechanisms by which acoustical energy is transferred to other types of energy, including heat, during the propagation through mud. Such mechanisms are envisioned as being viscous mechanisms and relaxation mechanisms. The latter might includethe breaking and reforming of bonds between clay particles. The work will lead to predictive analytical/computational models for the attenuation coe cient as a function of frequency for compressional and shear waves. The work will also include a development of analytical models that explain the depth-dependence of material and acoustic properties, including the material density and the frequency-dependence of wave speeds and attenuation. It is intended thatthe developed theory to provide an improved basis and improved methodologies for inverse methods for determination of speci c parameters and pro les associated with mud sediments at the bottom of the ocean. It is intended to develop a theoretical framework that relates commonly reported core-sampled data (including porosity, solid particle content, and particle size distributions) to an inferred and acoustically-tested model of the sediment structure.The proposed work also will develop a quantitative theory for predicting the circumstances under which bubbles will be present in mud samples, and it will develop a quantitative theory for the shapes, orientation, and size distributions of bubbles in mud. This will be extended to include a quantitative assessment of the e ects of bubbles in mud on the acoustic detection and classi cation of objects buried in mud. It is also proposed to develop a quantitative theory forhow organic matter a ects acoustic propagation and how larger organic objects might scatter sound and a ect the propagation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812439
Entities
People
- Allan Pierce
Organizations
- Office of Naval Research
- United States Navy