Some further work on a finer Ottawa sand were in fair agreenaent 

 although of somewhat faster velocity. This is probably due to a lower porosity 

 rather than smaller grain size. 



Summarizing the work on dry Ottawa sand, we find that the void ratio 

 or poi'osity exerts the principal effect on sound velocity, which for normally consoli- 

 dated samples is a manifestation of the confining pressures. 



b. Saturated Calcium Carbonate Clay Size Samples 



A series of tests on core no. 2 of the TOTO cores, including static 

 confined compression (consolidation), static triaxiaJ shear tests, torsional vibration 

 tests, and sound velocity tests, were performed on a saturated calcium carbonate 

 clay in order to reveal any correlation of the various soil moduli. Fig. 5. Table 1 

 presents the numerical data associated with Fig. 5. It is known that soils stressed 

 rapidly can exhibit properties quite unlike those observed under static conditions. 

 Further, in this series, because of the limitations of the equipment, some of the 

 moduli were entirely constrained, some unconfined, and some isotropically confined. 

 Nevertheless, the results are quite informative and interesting. 



c. Static Confined Moduli 



The compression moduli determined from a drained consolidation test 

 were quite low since strains are relatively large. These values, as shown in Fig. 5, 

 are many orders of magnitude away from the seismic moduli and, except for the 

 lateral confinement, bear little resemblance to the behavior under seismic pulses. 



d. Triaxial Shear Test 



The modulus of an isotropically confined triaxial sample is deter- 

 mined by applying an axial stress undrained. The separation of the elastic strain 

 from the secondary strain or creep is desirable. The method used was a repetitive 

 axial loading and unloading until a constant relation of stress to strain was obtained 

 (Fig. 6). This can be considered the static modulus of elasticity. The clay triaxial 

 samples were consolidated in steps from 1. 5 to 2 psi before the axial pressures 

 were applied; the resulting moduli vary almost linearly with confining pressure. 



e. Torsional Vibration 



This device, similar to that used by the investigators Wilson and 

 Dietrich (1960) was used to obtain the resonant torsional frequency. The samples 

 used were entirely imconfined and saturated and had been previously consolidated to 

 some confining pressure. The dynamic torsional modulus. 



387 



