Investigations of Sediment Properties in Sonar Bottom Reflectivity Studies

摘要

The objective of the investigation of sediment properties in acoustic bottom loss studies is to develop a capability to predict acoustic energy loss in various types of ocean depositional areas. This capability is being developed primarily by laboratory experiments on sediment samples and by model studies, utilizing laboratory-derived values of sediment properties. The data presented are the result of analyses performed on five cores taken from the Tongue of the Ocean, in an area less than two miles in diameter. The elastic properties of these soils were investigated by means of longitudinal and torsional wave vibration apparatus, confined compression tests, and static triaxial shear tests. The results of a pilot study indicate that the stress-strain relationship for static and dynamic loading of confined or unconfined homogeneous soil samples is considerably influenced by the void ratio or confining pressures. This results in a general trend of increasing modulus with depth. However, variations occurring in the corresponding vertical sound velocity profiles indicate that other parameters are influencing the sound velocity structure. Therefore, the object of primary concern is to determine the relationships between the structural and behavioral properties of the soil aggregate and its elastic moduli. (Author)