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Data report: consolidation state and stress ratio of clay-rich sediments from Site U13201

Maria Ask2


Overpressure and fluid flow processes in the deepwater Gulf of Mexico were investigated during Expedition 308 of the Integrated Ocean Drilling Program.

This data report presents the results from a reconsolidation test that was carried out on a clay-rich sample from the base of Brazos-Trinity Basin IV, at 276.40 m below seafloor. The sample was subjected to a stress path of uniaxial strain (K0 reconsolidation), and the test was conducted in an advanced triaxial cell under drained conditions. Posttest investigation revealed that the sample was disturbed by drilling. The results should be interpreted with care.

The sample was loaded to a total effective vertical stress, σv′, of 24 MPa, corresponding to effective horizontal stress, σh′, of >16 MPa and vertical strain, εv, of 16%. The results propose an effective vertical yield stress of 2.03 MPa, which suggests a maximum pore fluid pressure in excess of hydrostatic water pressure of 0.24 MPa. Furthermore, the ratio between effective horizontal and vertical stresses is rather constant, ~0.7, even at high stress magnitudes.

1 Ask, M., 2009. Data report: consolidation state and stress ratio of clay-rich sediments from Site U1320. In Flemings, P.B., Behrmann, J.H., John, C.M., and the Expedition 308 Scientists, Proc. IODP, 308: College Station, TX (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.308.207.2009

2 Department of Civil and Environmental Engineering, Division of Mining and Geotechnical Engineering, Luleå University of Technology, SE-971 87 Lul, Sweden.

Initial receipt: 5 March 2008
Acceptance: 12 January 2009
Publication: 6 May 2009
MS 308-207