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Ikari, Matt J; Kopf, Achim J (2015): (Table 1) Experimental details and results. PANGAEA, https://doi.org/10.1594/PANGAEA.858756, Supplement to: Ikari, MJ; Kopf, AJ (2015): The role of cohesion and overconsolidation in submarine slope failure. Marine Geology, 369, 153-161, https://doi.org/10.1016/j.margeo.2015.08.012

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Abstract:
Factor-of-safety analyses of submarine slope failure depend critically on the shear strength of the slope material, which is often evaluated with residual strength values and for normally consolidated sediments. Here, we report on direct measurements of both shear strength and cohesion for a quartz–clay mixture over a wide range of overconsolidation ratios (OCRs). For normally consolidated sediment at low stresses, cohesion is the dominant source of shear strength compared to friction. Significant increases in peak shear strength occur for OCR > 4, and the primary source of this strength increase is due to increased cohesion, rather than friction. The proportion of added shear strength due to cohesion depends log-linearly on the OCR. We show that at shallow depths where OCR values can be high, overconsolidated clays can be stronger than pure or nearly pure quartz sediments, which are cohesionless under near-surface conditions. Our data also suggest that areas which have experienced significant unroofing due to previous mass movements are less likely to experience subsequent failure at shallow depths due to increased peak strength, and if failure occurs it is expected to be deeper where the OCR is lower. In seismically active areas, this is one potential explanation for the general observation of lower slope failure recurrence compared to rates expected from triggering due to local earthquakes.
Comment:
GT = Grüne Tonerde, SQ = silt quartz, NC = normally consolidated, OC = overconsolidated.* Tau as measured in B126.
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1ExperimentExpIkari, Matt J
2Sample materialSample materialIkari, Matt J
3CommentCommentIkari, Matt JTest
4Normal stressSigmaNkPaIkari, Matt JDirect shear apparatus (GIESA, Germany)Consolidation
5Normal stressSigmaNkPaIkari, Matt JDirect shear apparatus (GIESA, Germany)Shearing
6DEPTH, sediment, experimentDepth expmIkari, Matt JDirect shear apparatus (GIESA, Germany)Geocode – Simulated maximum burial depth (mbsf)
7DEPTH, sediment, experimentDepth expmIkari, Matt JDirect shear apparatus (GIESA, Germany)Geocode – Simulated depth of failure (mbsf)
8Overconsolidation ratioPc/PoIkari, Matt JDirect shear apparatus (GIESA, Germany)
9Shear stressTaukPaIkari, Matt JDirect shear apparatus (GIESA, Germany)Peak
10Shear stressTaukPaIkari, Matt JDirect shear apparatus (GIESA, Germany)Residual
11CohesionCkPaIkari, Matt JDirect shear apparatus (GIESA, Germany)
12CohesionCkPaIkari, Matt JDirect shear apparatus (GIESA, Germany)Sliding cohesion
13CohesionC%Ikari, Matt JDirect shear apparatus (GIESA, Germany)component of shear stress attributed to sliding cohesion
14Friction coefficientµIkari, Matt JDirect shear apparatus (GIESA, Germany)Peak, apparent coefficient of friction
15Friction coefficientµIkari, Matt JDirect shear apparatus (GIESA, Germany)Residual, apparent coefficient of friction
16Residual friction coefficientµresIkari, Matt JDirect shear apparatus (GIESA, Germany)of sliding cohesion
17Cohesion coefficientC coefIkari, Matt JDirect shear apparatus (GIESA, Germany)Chi
18DisplacementDISmmIkari, Matt JDirect shear apparatus (GIESA, Germany)at cs measurement
19Residual friction coefficientµresIkari, Matt JDirect shear apparatus (GIESA, Germany)
20Friction coefficientµIkari, Matt JDirect shear apparatus (GIESA, Germany)Peak
Size:
525 data points

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