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doi:10.2204/iodp.proc.333.202.2014

Results

Compressional wave velocity as a function of effective pressure is shown in Figure F6 and Table T1. The compressional wave velocities from Sites C0011 and C0012 range from ~1480 to ~1680 m/s and ~1500 to ~1620 m/s, respectively, at low effective pressure up to 460 kPa. The velocities for Site C0011 and C0012 under in situ effective pressure condition vary from ~1510 to ~1770 m/s and ~1510 to ~1680 m/s, respectively. Velocity increases with effective pressure. Samples from deeper portions represent higher compressional wave velocity at in situ effective pressure conditions except for the one from Section 333-C0011D-31X-5, which has higher velocity than the others although the depth is in the middle part of the measured samples. Slopes of curves of velocity as a function of effective pressure are higher for shallower samples than for deeper samples.

Change in porosity during experiments as a function of effective pressure is shown in Figure F7 and Table T1, except for Sample 333-C0012C-11H-4 because the change in pore volume was not obtained for the sample. Porosity of tested samples from Sites C0011 and C0012 ranges from ~0.64 to ~0.50 and ~0.72 to ~0.48, respectively, at lower effective pressure. Porosity under in situ effective pressure for Sites C0011 and C0012 varies from ~0.61 to ~0.47 and ~0.69 to ~0.45, respectively. Porosity decreased with effective pressure increment during our experiments. The slopes of the curves of porosity and effective pressure space are comparable except for Sample 333-C0011D-31X-5 (Fig. F7).

The relationship between compressional wave velocity and porosity is represented in Figure F8. Two curves shown as “EJ98 high consolidation” and “EJ98 normal consolidation” in indicate the global relationship between compressional wave velocity and porosity (Erickson and Jarrard, 1998). Onboard porosity and compressional wave velocity (z-direction) for Holes C0011D and C0012A (drilled during Expedition 322) are also represented in Figure F8. The slope angles for each sample in the relationship between compressional wave velocity and porosity almost match the EJ98 normal consolidation curve except for Sample 31X-5. The exception of Sample 31X-5 is probably due to irregular deformation of the sample in the test (rubber jacket was partly stuffed in the edge of sample). Most samples from Sites C0011 and C0012 show slightly slower compressional wave velocity than EJ98 normal consolidation curves and onboard measurements, especially in the lower effective pressure (in porosity higher than ~0.6). The differences between velocities from laboratory experiments and onboard measurements are up to 50 m/s. The velocity in lower porosity is relatively consistent with that from onboard measurements and the EJ98 normal consolidation curve. The comparison of compressional wave velocities with depth between laboratory experiments, onboard measurements, and logging while drilling (LWD) for Site C0012H conducted during Expedition 338 is shown in Figure F9. Slightly slower velocities for shallower samples are also observed in the interval shallower than 100 m CSF. The samples deeper than 100 m, however, have relatively well-consistent velocities with those from onboard measurements and LWD.

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