precise measurement of reflection energies, termed the reflection coeffi- 

 cient, have been attempted with some success, but sediment types cannot 

 consistently be categorized, even broadly as clay, silt, or sand, largely 

 because of the rather widespread phenomenon of surficial sediment-entrapped 

 gas which produces a too-high reflection coefficient for the host sediment. 



Three approaches to the problem are indicated: (1) the development 

 of shear wave determination techniques for a rapid measurement of sedi- 

 ment shear strength, (2) a more comprehensive and quantitative analysis 

 of the information of engineering value contained in the bottom-reflected 

 pulse, and (3) the development of a deep-towed, high-resolution subbottom 

 profiler. 



Shear wave measurements cannot be made underway, disqualifying this 

 approach for site reconnaissance purposes. 



The second approach is being pursued, notablv at the Naval Undersea 

 Research and Development Center, San Diego, California and jointly by 

 Raytheon Company-University of New Hampshire. 



The third approach has not been vigorously pursued due primarily to 

 the limited number of potential users. The requirement to conduct sub- 

 bottom profiling over small construction sites in water depths to 6,000 

 feet is not widespread and so has been bypassed by industry. 



It is proposed that a self-powered, deep-towed subbottom profiler be 

 designed and fabricated which will produce high resolution records of at 

 least the first 100 feet of soil in water depths to 6,000 feet. 



Approved for public release; distribution unlimited, 



MBL/WHOI 



D D301 QDMDBM2 h 



iii 



