For fully saturated or nearly saturated samples this relationship is 

 too sensitive to slight variations of Poisson's ratio to be useful. For instance the 

 proper relationship between M and E in these tests result in v = 0.495. A true 

 test to the relation between the various moduli would have to come from dry or 

 partially saturated samples of known Poisson's ratio. Sediment samples are rarely 

 completely homogeneous, and therefore a range of moduli results. 



Conclusions Drawn from Moduli Tests on the Clay Samples 



The following conclusions can be drawn from this study: 



a. The stress-strain relationship for static and dynamic loading for confined 

 or unconfined soil samples is considerably influenced by the void ratio or confining 

 pressures. 



b. Young's modulus for soil may be determined by static triaxial tests or 

 dynamic vibration test. 



c. The theoretical relationship between constrained modulus and unconstrained 

 modulus E may be quite valid, but requires further investigation. 



d. In the determination of field sound velocity within a homogeneous strata, 

 the propagation of the acoustic wave should be primarily the function of void ratio 

 or confining pressure, and a short term field load or penetration test should be a 

 valid indicator of the velocity. 



Structural Properties 



Vertical profiles of several engineering properties, sound velocity, and 

 impedance for TOTO cores 5 and 6 are shown in Figs. 7 through 9. The numerical 

 data are presented in Tables 2 and 3. The lithologic structure of the cores, based 

 upon Shepard's triangular diagram are shown in Fig. 1. A plot of these structural 

 features indicates that there is a predominant advancing of coarse material from 

 the northwest and later regression. 



Note the trend toward increasing sound velocity with depth, which is similar 

 to that of the moduli with increasing pressure. The velocity profiles then indicate 

 that factors other than the void ratio, or confining pressure, are affecting the sound 

 velocity. Note also that core no. 6 does not reveal an apparent reason for the large 

 increase in velocity in the 3- to 4-foot layer. Similarly, these properties are 

 affecting the elastic moduli. Therefore, the object of immediate concern is to 

 determine the relationships between the engineering properties and the elastic moduli 

 of the saturated marine sediments. 



392 



