Gallagher 



.2- 

 ?4- 



-1 — I — r — I — r 



Zlxio'l 

 30 52 56 38 40 42 44 46 48 50 52 



^ 



T 



7 



IMPEDANCE «10* LB/FT -SEC 

 HAP CORE NO. 1 



Fig. 1 



Vertical Acoustic Impedance Profiles — 



Core No. I - HAP 



measured sound velocity values for 

 core no. 2, and for core no. 3, which 

 is not included in this report, were 

 determined with the same equipment, 

 and both were lower. It is interesting 

 to note that the laboratory vane shear 

 strength values for core no. 1 were an 

 order of magnitude higher than those 

 determined from cores 2 and 3. During 

 the core sampling operation it was 

 noted that the bottom was quite hard 

 in this general area. Core no. 1, in 

 particular, seemed so compact that it appeared to be almost dry when it was 

 removed from the barrel at sea. However, the porosities did lie in the 70 per- 

 cent range. The 3.7 kHz acoustic field data substantiate the nonuniformity 



of this bottom. 



Figure 1 denotes the impedance 

 profiles for the directly measured and 

 Sutton derived data for core no. 1. 

 The number and thicknesses of the 

 acoustic impedance layers are not 

 altered by the sound velocity differ- 

 ences, but differences in the magni- 

 tudes of these layers are produced. 

 The resulting differences in the peak 

 amplitude reflection coefficients over 

 increasing incident angles for core 

 requirements imposed on this model study, 

 dered significant. This is generally true 



10 20 30 40 50 60 70 80 9C 



°" ANGLE OF INCIDENCE (DEGREES) 



Fig. 2 



Reflection Coefficients versus Incident 



Angles- Core No. I -HAP 



no.] are shown in Fig. 2. Considering the 

 the differences in bottom loss are consi 

 for the succeeding data to be discussed 



The measured and Sutton derived 

 sound velocities and impedance data 

 are indicated in Table 2. Graphical 

 differences in the impedance profiles 

 are shown in Fig. 3. For core no. 2, 

 the differences in the sound velocity 

 values obtained from the two cases 

 of interest produced differences in 

 both the layering and the magnitudes 

 of the impedance layers. The reflec- 

 tion coefficients computed from the 

 measured and Sutton derived data for 



IMPEDANCE -I0*LB/FT'-SEC 



HAP CORE NO. 2 j 



INFERRED CURVE |N0 DATA AVAILABLE) 



Fig. 3 



Vertical Acoustic Impedance Profiles — 



Core No. 2 -HAP 



I 



93 



