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doi:10.2204/iodp.proc.322.203.2012

Results

All consolidation data are plotted in Figures F3, F5, F6, F7, F8, F9, F10, F11, F12, F13, and F14 together with best fit regression lines of compression indexes, maximum past effective stress constructions, and hydraulic conductivities as a function of void ratio. The equations of the fitted regression lines of compression indexes are presented in Table T2. Computed in situ vertical hydrostatic effective stresses, maximum past effective stresses, OCRs, in situ void ratios, regression equations for hydraulic conductivities, and in situ intrinsic permeabilities are presented for silty claystones (Table T3) and sandstones (Table T4) separately. All nomenclature is provided in Table T5. Data of all consolidation experiments are also available as supplementary material (see CONSOL in “Supplementary material”).

The consolidation properties document a significant difference between silty claystone and sandstone samples: clay-rich lithologies have higher compressibilities and lower in situ intrinsic permeabilities (Fig. F15). Recompression indexes of claystones range from 0.0222 to 0.0557, and compression indexes range from 0.4829 to 0.6905. Elastic compression is twice as high as recompression indexes, with values of 0.0663–0.1338. Maximum past effective stresses suggest that samples from lithologic Units II and III are slightly overconsolidated with OCRs of 1.22–1.23. In contrast, samples from Units IV and V are significantly overconsolidated with OCRs values of 2.06 and 2.51, respectively. Calculated hydraulic conductivity data from consolidation tests reveal a log-linear decrease as a function of void ratio. Void ratios of intact samples are at low stresses between 0.8132 and 1.11593 and decrease to 0.5983–0.4599 throughout the tests. Associated hydraulic conductivities are from 3.4 × 10^–9 to 7.5 × 10^–11 m/s and from 2.0 × 10^–13 to 6.3 × 10^–14 m/s, respectively. In situ intrinsic permeabilities decrease with depth from 1.8 × 10^–17 m² at 377.81 m CSF to 8.5 × 10^–20 m² at 749.38 m CSF, consistent with a decreasing in situ void ratio with depth.

Compression indexes show less variability for sand-rich samples. Recompression indexes are generally small with values of 0.0245–0.0058, which are consistent with the elastic compression indexes. Compression indexes for primary consolidation are from 0.2257 to 0.4357, with the exception of Sample 322-C0011B-8R-3, 104–115 cm. Consolidation data for this sample are characterized by extremely high void ratios, which point to an erroneous data set. Yield stresses are high for all nonvolcanic sandstones, with values scattered between 6.91 and 12.61 MPa and associated OCRs varying between 1.85 and 3.61. The volcanic sandstones from Unit II yield at effective stresses of 2.21 to 3.35 MPa, which correspond to OCRs of 0.85 and 1.30, respectively.

Hydraulic conductivities computed from CRS tests for remolded sandstones follow a log-linear decrease with void ratio. Compared to the clay-rich samples, the log(K)-e functions of sandstone specimens show a similar change with void ratio but an offset in log(K₀) toward higher conductivities. Void ratios of intact sandstone samples have values of 1.6149–0.6712 at low stresses and void ratios of 0.8359–0.5256 at maximum applied stresses. Associated hydraulic conductivities have values of 1.3 × 10^–7 to 1.0 × 10^–9 m/s and 3.8 × 10^–9 to 5.8 × 10^–11 m/s, respectively. In situ intrinsic permeabilities scatter between 4.0 × 10^–17 and 1.3 × 10^–15 m².

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