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Mechanical and hydraulic properties of Nankai accretionary prism sediments: Effect of stress path

Kitajima, H and Chester, FM and Biscontin, G (2012) Mechanical and hydraulic properties of Nankai accretionary prism sediments: Effect of stress path. Geochemistry, Geophysics, Geosystems, 13. ISSN 1525-2027

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Abstract

We have conducted triaxial deformation experiments along different loading paths on prism sediments from the Nankai Trough. Different load paths of isotropic loading, uniaxial strain loading, triaxial compression (at constant confining pressure, Pc), undrained Pc reduction, drained Pc reduction, and triaxial unloading at constant Pc, were used to understand the evolution of mechanical and hydraulic properties under complicated stress states and loading histories in accretionary subduction zones. Five deformation experiments were conducted on three sediment core samples for the Nankai prism, specifically from older accreted sediments at the forearc basin, underthrust slope sediments beneath the megasplay fault, and overthrust Upper Shikoku Basin sediments along the frontal thrust. Yield envelopes for each sample were constructed based on the stress paths of Pc-reduction using the modified Cam-clay model, and in situ stress states of the prism were constrained using the results from the other load paths and accounting for horizontal stress. Results suggest that the sediments in the vicinity of the megasplay fault and frontal thrust are highly overconsolidated, and thus likely to deform brittle rather than ductile. The porosity of sediments decreases as the yield envelope expands, while the reduction in permeability mainly depends on the effective mean stress before yield, and the differential stress after yield. An improved understanding of sediment yield strength and hydromechanical properties along different load paths is necessary to treat accurately the coupling of deformation and fluid flow in accretionary subduction zones. © 2012 American Geophysical Union All Rights Reserved.

Item Type: Article
Uncontrolled Keywords: Cam-Clay Critical state soil mechanics Nankai Permeability Stress Triaxial deformation
Subjects: UNSPECIFIED
Divisions: Div D > Geotechnical and Environmental
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:25
Last Modified: 08 Dec 2014 02:19
DOI: 10.1029/2012GC004124