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doi:10.2204/iodp.proc.308.204.2008 Laboratory testing resultsWe conducted CRSC tests on 9 samples from Site U1322 and 23 samples from Site U1324 in two laboratories (MIT and PSU). Table T3 summarizes the details of each CRSC test. Figures F4, F5, F6, F7, F8, F9, F10, F11, F12, F13, F14, F15, F16, F17, F18, F19, F20, F21, F22, F23, F24, F25, F26, F27, F28, F29, F30, F31, F32, F33, F34, and F35 show the consolidation curves in both e-log (σ′v) and ε-log (σ′v), normalized excess pore pressure, coefficient of consolidation (cv), SED, and hydraulic conductivity (K) for each CRSC test. The CRSC data sheet, which includes 12 columns (Table T4), can be found in Microsoft Excel format in “Supplementary material.” The compression index (Cc) refers to the slope of the normally consolidated portion of the compression curve in e-log (σ′v) space (Fig. F2). The compression behavior of the samples is similar at Sites U1322 and U1324 (Fig. F36). The measured values of cc range from 0.1508 to 0.5052. cc decreases with void ratio at both sites (Fig. F36). The expansion index (ce) refers to the slope of the unloading portion of the compression curve in e-log (σ′v) space. It ranges from 0.0153 to 0.1144 and also decreases with void ratio (Fig. F36). It must be noted that the expansion index varies with the amount of unloading that occurs. As such, the quoted expansion indexes are for unloading to an overconsolidation ratio of 10. The in situ hydraulic conductivity (Ki) is obtained by extrapolating the linear portion of the e-log (K) relation to the in situ void ratio. Values of Ki range from 2.18 × 10–11 to 6.38 × 10–10 m/s. Ki decreases with depth (Fig. F37). The ei-log (Ki) relations for sediments above and below 300 mbsf have different slopes (Fig. F37). Ki of the clayey silt sample (405.81 mbsf) is significantly higher than those of the silty clay samples, which reflects the lithology difference and stands out on the ei-log (Ki) plot (Fig. F37). The coefficient of consolidation, cv , ranges from 1.5 × 10–8 to 4.2 × 10–7 m2/s (Fig. F38). cv increases with depth for the sediments above 200 mbsf at both sites and shows no clear trend for the sediments below 200 mbsf. cv of the clayey silt sample (405.81 mbsf) is significantly higher than those of the silty clay samples, which reflects the lithology difference. The preconsolidation pressure, P′c, is determined using the work-stress method proposed by Becker et al. (1987). Figure F3 illustrates this approach for one sample (CRS802). P′c is significantly less than the hydrostatic vertical effective stress (σ′vh) at both sites (Fig. F39), which suggests that Ursa sediments are overpressured. |
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