Publication Date:
2019-01-23
Description:
We report the preliminary results of a triaxial and ring shear study
on clay-rich, fine-grained Pleistocene sediments cored in Ursa Basin,
Gulf of Mexico continental slope. Specimens from Integrated
Ocean Drilling Program (IODP) Expedition 308 Sites U1322 and
U1324 document friction coefficients in the range of 0.13–0.31,
with internal angles of friction of ~7.4°–17.2° in ring shear experiments.
At intermediate (7.624 MPa) to high (15.237 MPa) overburden
pressure, the majority of the samples tested show velocity
weakening, whereas lower overburden pressures do not give a
clear trend regarding velocity weakening or strengthening of the
samples. In consolidated-undrained triaxial tests, peak shear
stresses observed are between 27 and 140 kPa, with the strongest
sample by far coming from a core catcher section. We suspect that
this is an effect of fabric changes induced during hydraulic piston
coring. One sample coming from the base of a mass transport deposit
at Site U1322 is the weakest one tested. Young’s moduli calculated
range from 2 to 17.4 kPa. Stress paths indicate slight overconsolidation
of the samples, which is in line with the
information gained from preconsolidation stresses in other studies.
Permeability determined from consolidation data is in the
range of 10–16 to 10–17 m2, and hydraulic conductivity is around
10–9 to 10–10 ms–1. Grain density of the tested samples is around
2.7 g/cm3, and water content ranges from 18.3% to 30.7%.
Type:
Article
,
PeerReviewed
Format:
text
DOI:
10.2204/iodp.proc.308.211.2010
