Stress-regime-controlled yield and strength behavior of sediment from the frontal part of the Nankai accretionary prism.

Feeser, Volker, Moran, K. and Brückmann, Warner (1993) Stress-regime-controlled yield and strength behavior of sediment from the frontal part of the Nankai accretionary prism. Open Access Proceedings of the Ocean Drilling Program: Scientific Results, 131 . pp. 261-273.

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Abstract

Sediments undergoing accretion in trench-forearc systems are subjected to conditions of large lateral thrusting. This stress
regime controls the mechanism of faulting as well as the yield and strength properties of the sediment. Understanding them is
therefore crucial for the construction of quantitative models of sediment dynamics in convergent margin settings.
For this purpose triaxial and oedometer tests were performed on six whole-round core samples recovered from Site 808 from
depths between 173 and 705 mbsf. Samples from five depth intervals were subjected to a triaxial test program that was primarily
designed to define yield and strength behavior. Test specimens were cut parallel and normal to the core axis. Additional five
oedometer tests with similarly prepared specimens were performed on samples from four depth intervals to evaluate the directional
state and degree of sediment compaction.
Test results show that the degree of sediment compaction is higher than expected from overburden. This overcompaction
increases with depth. A well-developed mechanical anisotropy is evident in all samples tested, regardless of their depth and
lithology. Values of yield limit, stiffness, and shear strength are up to 40% higher in the horizontal direction compared to the
vertical direction. In addition the test data demonstrate that the axis of the volumetric yield loci have rotated into extensional stress
field. This verifies that the mechanical state of sediment in the accretionary wedge is controlled by in-situ stress conditions of
extensional nature. The coefficients of lateral stress inferred suggest that the extensional stress regime becomes increasingly
effective with depth.

Document Type: Article
Keywords: Nankai Trough, ODP Leg 131, sediments
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Kiel University
Refereed: No
Open Access Journal?: Yes
ISSN: 1096-7451
Projects: ODP
Date Deposited: 03 Mar 2016 10:04
Last Modified: 25 Oct 2016 12:07
URI: http://oceanrep.geomar.de/id/eprint/31682

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