Modelling the influence of strain localisation and viscosity on the behaviour of underground drifts drilled in claystone

Pardoen, Benoît; Collin, Frèdèric

doi:10.1016/j.compgeo.2016.05.017

Cited by 50 publications

(28 citation statements)

References 37 publications

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“…A comparison is made between the numerical results and experimental results of triaxial compression tests performed on laboratory specimen of COx clay rock (Armand et al 2017;Pardoen and Collin 2017). It must be emphasised that the numerical modelling are performed at the microscale of an EA and the experimental tests were realised on a macroscopic scale (not to mention the 3D effects that are not taken into account in the modelling).…”

Section: Micromechanical Properties and Responsementioning

confidence: 99%

Accounting for Small-Scale Heterogeneity and Variability of Clay Rock in Homogenised Numerical Micromechanical Response and Microcracking

et al. 2020

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Clayey rocks have a complex microstructure with multiple characteristic lengths. Deformation under mechanical loading generally induces damage by microcracking, which essentially concerns the scale of mineral inclusions embedded in the clay matrix. The modelling of these materials is considered within the framework of a double scale approach, by numerical homogenisation, of the squared finite element method type. This allows a heterogeneous microstructure of the material to be taken into account and a distribution of morphological properties to be introduced. Emphasis is placed on the generation of microstructures satisfying experimental observations, and keeping a certain simplicity to fit into the framework of double scale modelling. The material characteristics and behaviour are defined at the grain scale: the mineralogical properties include the mineral phase proportions and the grain morphology, while the material constituents are represented by elastic grains separated by damageable cohesive crack models. Then, the overall microscale behaviour of the material under solicitation is derived from equilibrated elementary area (EA) configuration and computational homogenisation. The variability of the material response is studied with regard to small-scale aspects as microstructure variability, microstructure size, grain angularity, and properties of grain contacts. Deformation anal-

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Section: Micromechanical Properties and Responsementioning

confidence: 99%

Accounting for Small-Scale Heterogeneity and Variability of Clay Rock in Homogenised Numerical Micromechanical Response and Microcracking

et al. 2020

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“…The time-dependent behaviour of COx claystone has been modelled by several authors using viscoplastic constitutive models (e.g. Shao et al 2003, Liu et al 2015, Pardoen and Collin 2016. For sake of simplicity, it was however preferred in a first attempt to adopt a basic viscoelastic Kelvin-Voigt rheological model made up of an elastic spring with bulk modulus K connected in parallel with a viscous damper of viscosity !…”

Section: 2! Effects Of Volumetric Creep On Thermal Strainsmentioning

confidence: 99%

Thermal Volume Changes and Creep in the Callovo-Oxfordian Claystone

et al. 2017

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International audienceThe Callovo-Oxfordian (COx) claystone is considered as a potential host rock for high-level radioactive waste disposal at great depth in France. Given the exothermic nature of radioactive wastes, a temperature elevation planned to be smaller than 100 °C will affect the host rock around the disposal cells. To gain better understanding of the thermal volumetric response of the COx claystone, a new thermal isotropic compression cell was developed with particular attention devoted to monitoring axial and radial strains. To do so, a high-precision LVDTs system ensuring direct contact between the LVDT stem and the claystone sample through the membrane was developed. A short drainage length (10 mm) was also ensured so as to allow full saturation of the sample under stress conditions close to in situ, and fully drained conditions during compression. High-precision strain monitoring allowed to observe a volumetric creep under stress conditions close to in situ. A drained heating test under constant stress carried out afterwards up to 80 °C exhibited a thermoelastic expansion up to a temperature of 48 °C, followed by thermoplastic contraction at higher temperature. Creep volume changes, that appeared to be enhanced by temperature, were modelled by using a simple Kelvin–Voigt model, so as to estimate the instantaneous response of the COx claystone and to determine its thermal expansion coefﬁcient. The temperature at which the transition between thermal expansion and contraction appeared is close to the maximum burial temperature of the Callovo-Oxfordian claystone, estimated at 50 C. This is in agreement with what has been already observed on the Opalinus Clay by Monfared et al. (2012) that was interpreted as a thermal hardening phenomenon, showing that the material kept the memory of the highest temperature supported during its geological history

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“…However, for strongly discontinuous, heterogeneous and non-linear granular material, the discrete simulations are becoming more popular and widely used [11][12][13][14]. The shear strain localization phenomena around geotechnical structures were studied in [15,16]. Since continuum models can be used on a global scale (real engineering problems), the discrete approaches are more suitable for grain-level behaviour study.…”

Section: Introductionmentioning

confidence: 99%

3D DEM simulations of basic geotechnical tests with early detection of shear localization

Grabowski

Nitka

2020

Studia Geotechnica Et Mechanica

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This paper deals with elementary geotechnical tests: triaxial and direct shear of cohesionless sand using the discrete element method (DEM). The capabilities of the numerical DEM code are shown, with a special focus on the early phenomena appearance in localization zones. The numerical tests were performed in 3D conditions with spherical grains. Contact moments law was introduced due to simulate not perfectly round sand grains. The influence of different physical parameters was studied, e.g. initial density or confining pressure. The sieve curve corresponded to the Karlsruhe sand [1]; however, in some tests, it was linearly scaled. Special attention was laid on the behaviour of the sand grains inside localization, e.g. rotation, porosity, fluctuations, etc. and forces redistribution. Emphasis was given on the pre-failure regime and early localization predictors.

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Modelling the influence of strain localisation and viscosity on the behaviour of underground drifts drilled in claystone

Cited by 50 publications

References 37 publications

Accounting for Small-Scale Heterogeneity and Variability of Clay Rock in Homogenised Numerical Micromechanical Response and Microcracking

Accounting for Small-Scale Heterogeneity and Variability of Clay Rock in Homogenised Numerical Micromechanical Response and Microcracking

Thermal Volume Changes and Creep in the Callovo-Oxfordian Claystone

3D DEM simulations of basic geotechnical tests with early detection of shear localization

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