University of California-Santa Cruz, United States

We conducted constant rate of strain consolidation tests on 9 samples from Integrated Ocean Drilling Program Site U1322 and 23 samples from Site U1324 in three laboratories (Massachusetts Institute of Technology, Pennsylvania State University, and Rice University) to obtain the consolidation properties of the sediment, as well as determine the stress history of the sites. The sediments recovered from above 200 meters below seafloor (mbsf) at both sites have similar consolidation properties. The compression index (Cc) ranges from 0.1508 to 0.5052. Cc decreases with void ratio at both sites. The expansion index (Ce) ranges from 0.0153 to 0.1144 and decreases with void ratio at both sites. The in situ hydraulic conductivity (Ki) ranges from 2.18X10 (super -11) to 6.38X10 (super -10) m/s. Ki decreases with depth. The e-log(Ki) relation has different slopes for sediments above and below 300 mbsf at Site U1324. The coefficient of consolidation (cv) ranges from 1.5X10 (super -8) to 4.2X10 (super -) 7 m (super 2) /s. cv increases with depth for the sediments above 200 mbsf at both sites and shows no clear trend for the sediments below 200 mbsf at Site U1324. The preconsolidation pressure (P'c) is significantly less than the hydrostatic vertical effective stress (sigma 'vh) at both sites, which suggests that Ursa sediments are overpressured.