SBIR-STTR Award

In this research, a miniature computer based chirp sonar will be developed for making rapid surveys of offshore sediments. The sonar reflection data will be integrated to both differential GPS navigation and spot geotechnical measurements in a manner that will provide rapid large scale assessment of marine soil properties. The cumulative survey results will be presented, in real time, in the form of computer generated contour maps detailing dediment property variations in density, prosity, and shear strength. A large portion of the sonar system development will be extracted from our Navy sponsored research 6(biography). Minimal new research is needed for the actual sonar hardware component of this development effort. The new research that is needed and proposed will focus on developing the interface between the acoustic measurements and geotechnical measurements taken from such devices as penetrometers, instrumented cones, vibratory corers, and other devices. At selected site locations, the data from these measurements will be entered as ground truth into the system computer model. The ground truth data is used in the computer program to calibrate the models that relate acoustic impedance to sediment properties 6. This research will result in the design of a commercial low cost combined acoustic/geotechnical instrument that will perform rapid material resource assessment, pollution monitoring, and provide data for marine construction design.

An integrated geotechnical - acoustic sediment property measurement system that generates survey maps of geotechnical and other physical sediment properties will be developed by integrating a retrievable penetrometer with a X-Star high resolution subbottom profiler. X-Star profilers can generate maps of geoacoustic properties from normal incidence reflection data and DGPS navigation data. By adding a penetrometer to an X-Star sonar, geotechnical properties can also be measured and compared to acoustic measurements. At a few selected locations in a X-Star survey area, penetrometer data is collected to estimate geotechnical properties. The acoustic and geotechnical property data are used to generate the empirical interrelationships which are used to convert maps of acoustic properties to a map of a geotechnical property. For example, Phase I showed that the X-Star bottom loss measurements could be converted to a map of shear strength with just 2 or 3 penetrometer measurements. The Phase II work includes integrating the penetrometer/X-Star system and extensive field testing to determine the accuracy of estimating geotechnical and other physical sediment properties. The penetrometer and acoustic reflection data will be digitized and analyzed by the X-Star topside processor. Impedance profiles generated from reflection data will be compared to shear strength profiles predicted from penetrometer velocity data.