Towards this end it is intended to artifically sediment core samples with 

 known grain sizes, grain shapes, and mineral characteristics in the cohesionless 

 and cohesive soil types. If these properties are held constant, the normality and 

 temperature of the i^eceiving water will be varied to obtain differences in settling 

 characteristics and, therefore, structure. Also, the degree of sorting will be 

 varied to obtain varying degrees of stiffness. These samples will then be subjected 

 to the various tests for determinations of the moduli. An interesting experiment in 

 this regard will be to determine the moduli while holding the void ratio constant and 

 varying the confining pressure. 



Essentially, the measure of compressibility reveals the relative ability of 

 the soil to resist shear. Measurements of shear strength then should be linked with 

 those of elastic moduli. I^ooking at the associated data required for effective shear 

 strength measurements, such as void ratio, friction coefficient, over-consolidation 

 ratio, temperature, strain and rate of strain, and cohesion, it can be seen that these 

 properties are very similar to those required for interpreting moduli measurements. 

 Therefore, it can be inferred, at this time, that a shear strength determination 

 w ould be the most effective single indicator of the elastic moduli and, thus, longi- 

 tudinal sound velocity. The shear strength also can be related to shear velocity. 



This study may lead to a more intensive investigation of the cohesive or 

 physio-chemical characteristic of the fine grained sediments and its relationship to 

 acoustic behavior. 



CONSIDERATION OF BEHAVIORAL CHARACTERISTICS 



It was noted in several of the Bermuda cores that the median grain size deter- 

 minations revealed a predominantly silt layer, whereas the atterberg tests indicated 

 that the sediment aggregate behaved like a clay. The degree of deflocculation of the 

 fine silt and clay particles can not always be accurately determined. This usually 

 results in larger particle diameter size than that which actually exists. Also, in- 

 accuracies are inherent in the application of Stokes' Law to this measurement, since 

 the particle shape is assumed to be spheroidal. Perhaps we should focus our atten- 

 tion on the behavioral characteristics of the sediment mass. Should we explore the 

 action and reaction between the acoustic wave stress and the soil particle as a con- 

 tributing factor in energy absorption? It is the opinion of the authors that this well 

 may be the most fundamental approach to the problem, and therefore we shall attempt 

 to devote some study to the cohesive characteristics of the sediments. Since little 

 absorption occurs in the cohesionless sediments, perhaps this approach is justified. 



When the subject of pore water in the clay aggregate is discussed, is the double 

 layer water, which may occupy a large portion of the volume of the aggregate, 

 considered? It is quite likely to assume that this water will not subscribe to the 

 alteration of temperature and pressure when the sample is raised to the surface, as 



398 



