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doi:10.2204/iodp.proc.322.203.2012 Data report: consolidation properties of silty claystones and sandstones sampled seaward of the Nankai Trough subduction zone, IODP Sites C0011 and C00121Andre Hüpers2 and Achim J. Kopf2AbstractWe conducted incremental loading and constant rate of strain consolidation tests on sediments recovered during Integrated Ocean Drilling Program (IODP) Expedition 322 from Sites C0011 and C0012, located seaward of the deformation front in the Nankai Trough subduction zone, southeast Japan. In total, five silty claystones and six sandstone samples from lithologic Units II–V were tested. The results document higher compressibilities for clay-rich specimens with compression indexes of Cc = 0.4829–0.6905, whereas sandstones are characterized by values of Cc = 0.2257–0.4357. Maximum past effective stresses of silty claystones from Units II and III suggest a normal to slightly overconsolidated state. Samples from Units IV and V are significantly overconsolidated with overconsolidation ratios of 2.06–2.51. Vertical effective stresses of ~10 MPa are needed to force yielding nonvolcanic sandstones. These yield stresses are significantly higher than the calculated value of in situ hydrostatic vertical effective stresses. In contrast, volcanic sandstones yield at stresses close to the in situ hydrostatic effective stress. For all tested specimens, the logarithm of hydraulic conductivity K shows a linear relationship with void ratio, with sandstones exhibiting higher K values. Calculated in situ intrinsic permeabilities for silty claystones decrease with depth from 1.8 × 10–17 m2 at 377.81 m core depth below seafloor (CSF) to 8.5 × 10–20 m2 at 749.38 m CSF. In situ intrinsic permeabilities of sandstones do not show a clear trend but scatter between values of 1.3 × 10–15 and 4.0 × 10–17 m2. |
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