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Peter Troch - One of the best experts on this subject based on the ideXlab platform.
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an improved calculation model for the wave induced Pore Pressure distribution in a rubble mound breakwater core
Coastal Engineering, 2012Co-Authors: Dieter Vanneste, Peter TrochAbstract:Abstract The spatial distribution of the wave-induced Pore Pressure height in the core of a conventional rubble-mound breakwater is studied in this work. Use is made of existing theoretical and experimental knowledge to establish a calculation model for the Pressure distribution on the front core slope and the attenuation of Pore Pressures within the breakwater core. The new model formulae are derived empirically and calibrated by means of a non-linear regression analysis of Pore Pressure measurements in a large-scale conventional breakwater model, under non-overtopping and non-breaking wave conditions. They relate the spatial distribution of Pore Pressure height to the sea state in front of the breakwater considering a homogeneous breakwater core, but do not contain any material properties related to the porous flow resistance. The new calculation model predicts the Pore Pressure distribution with higher accuracy than the existing method generally employed and is applicable in a broad range of wave conditions. The calculation model is validated with additional experimental data from Pore Pressure measurements on a small-scale model, confirming the capability of predicting the Pore Pressure height under varying wave conditions. The comparison between both models moreover provides insight into the general applicability of the calculation model.
David L Olgaard - One of the best experts on this subject based on the ideXlab platform.
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generation and maintenance of Pore Pressure excess in a dehydrating system 2 theoretical analysis
Journal of Geophysical Research, 1997Co-Authors: Tengfong Wong, Suzchung Ko, David L OlgaardAbstract:Fluid is released by dehydration reactions during prograde metamorphism. If the dilation of the Pore space is insufficient to provide storage for all the released fluid, then Pore Pressure excess is generated. Whether the excess can be maintained over long duration hinges on the hydraulic transport properties of the rock. Motivated by recent experimental and microstructural observations, we developed a theoretical model which incorporates dehydration and porosity production rates as source terms in the hydraulic diffusion equation. The permeability was assumed to be sensitively dependent on the porosity. The finite difference technique was used to analyze the generation and maintenance of Pore Pressure excess for several types of boundary conditions of importance in laboratory and crustal scales. Analytic estimates of the Pore Pressure anomaly were also obtained. The model is in reasonable agreement with experimental observations on dehydration-induced weakening and transient buildup of Pore Pressure in a nominally drained sample. It provides hydrogeological constraints on the development of Pore Pressure excess in metamorphic and tectonic settings. The maintenance of a nearly lithostatic Pore Pressure requires the permeability to be below a critical value which increases with increasing dehydration rate and thickness of the dehydrating layer, and with decreasing porosity production rate. If these constraints are not met, the Pore Pressure excess can only occur as a transient pulse, the amplitude of which may approach lithostatic for sufficiently large dehydration rate and layer thickness, or sufficiently low permeability.
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earthquakes as a coupled shear stress high Pore Pressure dynamical system
Geophysical Research Letters, 1996Co-Authors: Stephen A Miller, David L OlgaardAbstract:The migration, coalescence and localization of slip, seismicity, and zones of high Pore Pressure are modeled using a porosity reduction mechanism to drive Pore Pressure within a fault zone in excess of hydrostatic. Increased Pore Pressure in discrete cells creates zones of low effective stress, which induces slip that may propagate to surrounding cells depending on the local state of stress. At slip, stress is transferred using the solution for a rectangular dislocation in an elastic half-space, and Pore Pressures are redistributed by conserving fluid mass. Using simple assumptions about fault rheology and permeability, it is shown that the interaction between shear stress and effective stress evolves to a state of earthquake clustering with repeated events, locked zones, and large variations in fault strength. The model evolves from a uniform shear stress state on a strong fault, to a heterogeneous shear stress state on a weak fault.
Harold Tobin - One of the best experts on this subject based on the ideXlab platform.
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Hydrogeology and Mechanics of Subduction Zone Forearcs: Fluid Flow and Pore Pressure
Annual Review of Earth and Planetary Sciences, 2011Co-Authors: Harold TobinAbstract:At subduction zones, fluid flow, Pore Pressure, and tectonic processes are tightly interconnected. Excess Pore Pressure is driven by tectonic loading and fluids released by mineral dehydration, and it has profound effects on fault and earthquake mechanics through its control on effective stress. The egress of these overPressured fluids, which is in part governed by the presence of permeable fault zones, is a primary mechanism of volatile and solute transport to the oceans. Recent field measurements, new constraints gained from laboratory studies, and numerical modeling efforts have led to a greatly improved understanding of these coupled processes. Here, we summarize the current state of knowledge of fluid flow and Pore Pressure in subduction forearcs, and focus on recent advances that have quantified permeability architecture, fluxes, the nature and timing of transience, and Pressure distribution, thus providing new insights into the connections between fluid, metamorphic, mechanical, and fault slip proc...
Tetsuya Matsuda - One of the best experts on this subject based on the ideXlab platform.
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homogenized elastic viscoplastic behavior of anisotropic open porous bodies with Pore Pressure
International Journal of Solids and Structures, 2012Co-Authors: Kazutaka Ikenoya, Dai Okumura, Tetsuya MatsudaAbstract:Abstract Constitutive modeling is studied for the homogenized elastic–viscoplastic behavior of Pore-pressurized anisotropic open-porous bodies made of metallic base solids at small strains and rotations. For this purpose, by describing micro–macro relations relevant to periodic unit cells of anisotropic open-porous bodies subjected to Pore Pressure, constitutive features are discussed for the viscoplastic macrostrain rate in steady states. On the basis of the constitutive features found, the viscoplastic macrostrain rate is represented as an anisotropic function of Terzaghi’s effective stress, which is shown using Hill’s macrohomogeneity condition. The resulting viscoplastic equation is used to simulate the homogenized elastic–viscoplastic behavior of an ultrafine plate-fin structure subjected to uniaxial/biaxial loading in addition to Pore Pressure. The corresponding finite element homogenization analysis is also performed for comparison. It is demonstrated that the developed viscoplastic equation simulates well the anisotropic effect of Pore Pressure in the viscoplastic range in spite of there being no anisotropic factor and no fitting parameter in Terzaghi’s effective stress itself.
Kazutaka Ikenoya - One of the best experts on this subject based on the ideXlab platform.
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homogenized elastic viscoplastic behavior of thick perforated plates with Pore Pressure
Key Engineering Materials, 2013Co-Authors: Kazutaka Ikenoya, Noriko Takano, Naoto KasaharaAbstract:The homogenized elastic-viscoplastic behavior of thick perforated plates with Pore Pressure is investigated for macro-material modeling. To this end, the homogenized behavior is analyzed using a FE homogenization method of periodic solids. It is assumed that the base metal of perforated plates exhibits the elastic-viscoplastic behavior based on Hooke’s law and Norton’s power-law. The resulting homogenized behavior is simulated using an elastic-viscoplastic macro-material model developed for Pore-pressurized anisotropic open-porous bodies. It is shown that the macro-material model suitably represents the macro-anisotropy and macro-volumetric compressibility that are revealed by the FE homogenization analysis in the presence and absence of Pore Pressure.
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homogenized elastic viscoplastic behavior of anisotropic open porous bodies with Pore Pressure
International Journal of Solids and Structures, 2012Co-Authors: Kazutaka Ikenoya, Dai Okumura, Tetsuya MatsudaAbstract:Abstract Constitutive modeling is studied for the homogenized elastic–viscoplastic behavior of Pore-pressurized anisotropic open-porous bodies made of metallic base solids at small strains and rotations. For this purpose, by describing micro–macro relations relevant to periodic unit cells of anisotropic open-porous bodies subjected to Pore Pressure, constitutive features are discussed for the viscoplastic macrostrain rate in steady states. On the basis of the constitutive features found, the viscoplastic macrostrain rate is represented as an anisotropic function of Terzaghi’s effective stress, which is shown using Hill’s macrohomogeneity condition. The resulting viscoplastic equation is used to simulate the homogenized elastic–viscoplastic behavior of an ultrafine plate-fin structure subjected to uniaxial/biaxial loading in addition to Pore Pressure. The corresponding finite element homogenization analysis is also performed for comparison. It is demonstrated that the developed viscoplastic equation simulates well the anisotropic effect of Pore Pressure in the viscoplastic range in spite of there being no anisotropic factor and no fitting parameter in Terzaghi’s effective stress itself.
