Reactive plasticity for clays: application to a natural analog of long-term geomechanical effects of nuclear waste disposal

Hueckel, Tomasz; Pellegrini, R.

doi:10.1016/s0013-7952(01)00114-4

Cited by 40 publications

(9 citation statements)

References 32 publications

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“…The main drawback of the slip line field theory was that it cannot be used for rate and temperature dependent constitutive laws which significantly hampered the applicability to modern engineering applications since the importance of temperature is well known in constitutive properties of most materials. Soil, rocks and ceramics are significantly influenced by temperature with strain localisation being strongly affected by thermal loading [Hlickel and Baldi 1990;Htickel and Pellegrini 2002]. In polymers and polycarbonates temperature and strain rate are key parameters influencing the response of the material, even at ambient conditions [Bauwens-Crowet et al 1974].…”

Section: Introductionmentioning

confidence: 99%

Conditions for the localisation of plastic deformation in temperature sensitive viscoplastic materials

Paesold

Bassom

Regenauer-Lieb

et al. 2016

J. Mech. Mater. Struct.

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We study the onset of localisation of plastic deformation for a class of materials that exhibit both temperature and rate sensitivity. The onset of localisation is determined via an energy bifurcation criterion, defined by the postulate that viscoplastic materials admit a critical (mechanical) energy input above which deformation becomes unstable and plastic localisation ensues. In analogy to the classical concepts of mechanics, the conditions for the onset of localisation in temperature-sensitive viscoplastic materials are reached at a critical stress. However, it is shown that in viscoplastic materials a material bifurcation occurs when the heat supply through mechanical work surpasses the diffusion capabilities of the material. This transition from near-isothermal stable evolution to near-adiabatic thermal runaway is the wellknown concept of shear heating. Here, it is generalised and the correspondence between this runaway instability and the localisation of plastic deformation in solid mechanics is detailed. The obtained phase space controlling the localisation is shown to govern the evolution of the system in the postyield regime. These results suggest that the energy balance essentially drives the evolution of the plastic deformation and therefore constitutes a physics-based hardening law for thermoviscoplastic materials.

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Section: Introductionmentioning

confidence: 99%

Conditions for the localisation of plastic deformation in temperature sensitive viscoplastic materials

Paesold

Bassom

Regenauer-Lieb

et al. 2016

J. Mech. Mater. Struct.

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“…Such hypersurfaces are frequently used in constitutive modelling of geomaterials. [155][156][157][158] Unlike the evolution of internal variables, the temperature evolution is not obtained through experiments. Rather than that, it obeys the differential equation derived through the energy balance and the second law of thermodynamics.…”

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confidence: 99%

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Regenauer‐Lieb¹,

Veveakis²,

Poulet³

et al. 2013

j coupled syst multiscale dyn

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Geoscientists are confronted with the challenge of assessing nonlinear phenomena that result from multiphysics coupling across multiple scales from the quantum level to the scale of the earth and from femtosecond to the 4.5 Ga of history of our planet. We neglect in this review electromagnetic modelling of the processes in the Earth's core, and focus on four types of couplings that underpin fundamental instabilities in the Earth. These are thermal (T), hydraulic (H), mechanical (M) and chemical (C) processes which are driven and controlled by the transfer of heat to the Earth's surface. Instabilities appear as faults, folds, compaction bands, shear/fault zones, plate boundaries and convective patterns. Convective patterns emerge from buoyancy overcoming viscous drag at a critical Rayleigh number. All other processes emerge from non-conservative thermodynamic forces with a critical critical dissipative source term, which can be characterised by the modified Gruntfest number Gr. These dissipative processes reach a quasi-steady state when, at maximum dissipation, THMC diffusion (Fourier, Darcy, Biot, Fick) balance the source term. The emerging steady state dissipative patterns are defined by the respective diffusion length scales. These length scales provide a fundamental thermodynamic yardstick for measuring instabilities in the Earth. The implementation of a fully coupled THMC multiscale theoretical framework into an applied workflow is still in its early stages. This is largely owing to the four fundamentally different lengths of the THMC diffusion yardsticks spanning micro-metre to tens of kilometres compounded by the additional necessity to consider microstructure information in the formulation of enriched continua for THMC feedback simulations (i.e., micro-structure enriched continuum formulation). Another challenge is to consider the important factor time which implies that the geomaterial often is very far away from initial yield and flowing on a time scale that cannot be accessed in the laboratory. This leads to the requirement of adopting a thermodynamic framework in conjunction with flow theories of plasticity. This framework allows, unlike consistency plasticity, the description of both solid mechanical and fluid dynamic instabilities. In the applications we show the similarity of THMC feedback patterns across scales such as brittle and ductile folds and faults.

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“…Based on the experimentally reported thermoplastic response of clay minerals [ Hueckel and Baldi , ; Hueckel and Pellegrini , ] and artificial fault gouges [ Mair et al , ] the model was allowed the flexibility to demonstrate either thermal hardening or softening. Since we are interested in creeping faults, i.e., faults that could sustain large amount of deformations under the same stress conditions, the thermal dependency had to be counterbalanced by rate dependency, introduced as an antagonistic mechanism that would have the capability of inducing constant friction coefficient.…”

Section: Discussionmentioning

confidence: 99%

Thermo‐poro‐mechanics of chemically active creeping faults. 1: Theory and steady state considerations

2014

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In this paper, we study the behavior of a fluid‐saturated fault under shear, based on the assumption that the material inside exhibits rate‐ and temperature‐dependent frictional behavior. A creeping fault of this type can produce excess heat due to shear heating, reaching temperatures which are high enough to trigger endothermic chemical reactions. We focus on fluid‐release reactions and incorporate excess pore pressure generation and porosity variations due to the chemical effects (a process called chemical pressurization). We provide the mathematical formulation for coupled thermo‐hydro‐chemo‐mechanical processes and study the influence of the frictional, hydraulic, and chemical properties of the material, along with the boundary conditions of the problem on the behavior of the fault. Regimes of stable‐frictional sliding and pressurization emerge, and the conditions for the appearance of periodic creep‐to‐pressurization instabilities are then derived. The model thus extends the classical mechanical stick‐slip instabilities by identifying chemical pressurization as the process governing the slip phase. The different stability regimes identified match the geological observations about subduction zones. The model presented was specifically tested in the Episodic Tremor and Slip sequence of the Cascadia megathrust, reproducing the displacement data available from the GPS network installed. Through this process, we identify that the slow slip events in Cascadia could be due to the in situ dehydration of serpentinite minerals. During this process, the fluid pressures increase to sublithostatic values and lead to the weakening of the creeping slab.

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Reactive plasticity for clays: application to a natural analog of long-term geomechanical effects of nuclear waste disposal

Cited by 40 publications

References 32 publications

Conditions for the localisation of plastic deformation in temperature sensitive viscoplastic materials

Conditions for the localisation of plastic deformation in temperature sensitive viscoplastic materials

Multiscale coupling and multiphysics approaches in earth sciences: Applications

Thermo‐poro‐mechanics of chemically active creeping faults. 1: Theory and steady state considerations

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