fine-grained sediments, clays and silts, attenuate acoustic energy to a 

 lesser degree than coarser materials. Sound may, therefore, penetrate 

 clays more deeply than sands. 



Continuous reflection profiling can be, therefore, a most useful 

 tool for the marine construction engineer. Most importantly, the tech- 

 nique provides a detailed, accurate, and continuous profile of the sub- 

 surface geology not arrived at through other, more conventional techniques. 

 Secondly, seismic methods and a knowledge of the acoustic properties of 

 marine sediments provide quantitative data of the relative load-bearing 

 properties of a region. 



RECOMMENDATIONS FOR FUTURE RESEARCH 



It is suggested that research applicable to marine construction 

 engineering application be pursued in the following areas: 



1. Measurement of shear wave velocities in-situ and on 

 cores . 



2. In-depth study of the rheological properties of marine 

 sediments, including the relationship of the dynamic 

 Poisson's ratio (from seismic wave velocities) to the 

 static value; and the relationship of Poisson's ratio 

 at small (seismic) stresses to realistic, operating 

 stresses. 



3. Comprehensive analysis of the information of engineering 

 value contained in the bottom-reflected pulse. 



4. Investigate the feasibility and applicability of other, 

 nonacoustic remote methods to obtain rapid information 

 about the characteristics of a potential seafloor con- 

 struction site, with the aim to develop a complete, 

 rapid, and accurate site survey system. 



5. Design and fabricate a deep towable (to 6,000-foot depth), 

 self-powered 3.5 kHz seismic reflection profiler for obtain- 

 ing data over small, test sites. A seismic sound source 

 towed near the seafloor will provide high resolution whether 

 the echo events are picked up near the source or at the sur- 

 face. A self-powered source using surface hydrophones would 

 require no electrical cable but could be towed bv svnthetic 

 line . 



It would appear that this (number 5) would be the most cost-effective 

 approach towards advancing the state-of-the-art in profiling technology bv 

 providing a simple device to retrieve high-resolution, seismic reflection 

 data from great depths for the construction engineer. 



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