A NEW PORTABLE VELOCIMETER FOR SOUND SPEED MEASUREMENTS IN SANDY SEAFLOORS.

摘要

Many underwater applications require the knowledge of seafloor parameters. Depending of the application, the need is for different type of parameters: sonar performances depends on bottom reflection properties which are deduced from acoustic parameters; mine hunting capacities are linked to clutter which arises from geometry of seafloor surface; seismic analysis is based on detection of impedance contrast of buried interfaces; mechanical structure of seafloor is required for civil engineering,... The relations between those various defines the field of geoacoustic studies. Many efforts have been done for years (see e.g. [1-3]), in particular concerning the soft sediments of deep waters or rock reservoirs properties for offshore energy detection. Interest for coarser sediments as sands is more recent. Significant contribution have been done through in-situ experimentation, for example with SAX 99 [4] and SAX 04 campaign [5,6], through laboratory measurements (see e.g. [7]) and through theoretical modelling (see [3] and references therein). Nevertheless, these measurements and modeling have generally been conducted with fine or well-sorted sands or glass beads.