Laboratory investigation of the mechanical behaviour of Tournemire shale

Niandou, Halidou; Shao, Jian‐Fu; Henry, J.P.; Fourmaintraux, D.

doi:10.1016/s1365-1609(97)80029-9

Cited by 610 publications

(214 citation statements)

References 4 publications

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“…Does it suffice for sufficient fragmentation? For a crude assessment, consider that the material parameters of a typical unconfined shale are G = 15:1 GPa, τ 0 = 5 MPa, Γ = 100 N=m, ρ = 2;200 kg=m 3 (21)(22)(23). This yields B a ≈ 15 1, and thus suffices for comminution.…”

Section: Some Results and Discussionmentioning

confidence: 99%

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing

Bažant

Caner

2013

Proc. Natl. Acad. Sci. U.S.A.

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Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the −2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the −1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow.fracture mechanics | dynamic fracture | shale gas | dimensional analysis T he previous studies of high-rate dynamic fracture of rocks, concretes, ceramics, composites, and metals have dealt mainly with the nucleation, propagation, and branching of dynamically propagating cracks, their interference with elastic or shock waves, and the mechanism of development of the zones of densely distributed fractures, called the Mescall zones (1-7). However, a comminution model in the form of a macroscopic constitutive equation that could be used in large dynamic finite element programs for global response of structures is apparently still unavailable.Seeking such a constitutive model, we begin with the analysis of a simple idealized process in which the solid is comminuted to identical particles (Fig. 1). Among simple space-filling regular subdivisions in the plane of maximum shear, regular hexagons are the most likely because they give the smallest surface-to-volume ratio (Fig. 1A) and thus require the minimum energy to form. In the direction normal to the hexagons, we assume the particles to be prismatic.Consider that, at a certain moment, the strain rate (shown in Fig. 1B as a displacement regarded as infinitesimal) becomes high enough for the kinetic energy of shear strain rate to suffice for creating the fractures and interface slips that separate the particles of as yet unknown size. As that happens, the particles release their local kinetic energy, slip against each other, and regain their original undeformed shape, while the particle centers conform to the same macroscopic velocity field (Fig. 1C).For the sake of simplicity and clarity, we will first outline a 2D analysis of comminution in the plane of maximum shear strain rate denoted as _ e D , and leave the 3D generaliza...

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Section: Some Results and Discussionmentioning

confidence: 99%

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing

Bažant

Caner

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…In sedimentary rocks (like shales) there is typically a strong inherent anisotropy, which is the result of the presence of bedding planes (cf. Niandou et al [7]); the latter clearly visible at the macroscale. Whether inherent, induced or a combination of both, the anisotropy in microstructure may have a significant effect in the context of analysis and design of geotechnical structures.…”

Section: Introductionmentioning

confidence: 94%

Description of hydraulic and strength properties of anisotropic geomaterials

Pietruszczak¹,

Pande²

2012

Studia Geotechnica Et Mechanica

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Abstract:In this paper, a simple generalization of Darcy's law is proposed for the description of hydraulic properties of anisotropic porous materials. The coefficient of permeability is defined as a scalarvalued function of orientation. The principal directions of permeability are determined from a fabric descriptor specifying the distribution of average pore size. An example is provided for identification of material parameters, which is based on an idealized "pipe network model". A procedure for defining the anisotropy in strength properties, which incorporates a conceptually similar approach, is also reviewed and an illustrative example is provided.

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“…A comprehensive experimental program has been carried out on argillite (including Tournemire argillite and Meuse/HauteMarne argillite) at the Lille Laboratory of Mechanics, and the results have been reported by Niandou et al [23], Chiarelli et al [4] and Zhang et al [10]. A short summary of test data on argillite is given in this section, and these data will be used in Section 4 to validate the numerical predictions.…”

Section: Summary Of Experimental Investigationsmentioning

confidence: 99%

“…In this work, the triaxial tests are conducted on specimens with two inclinations of bedding planes of h = 0°and h = 60°, which correspond to shear failure and sliding failure and are used to determine the directional distribution of c and m, respectively. For the specimens at h = 0°, the axial loading direction is perpendicular to the bedding planes, and the failure is due to the shear band in the argillite matrix; the fracture angle may be assumed as equal to 70°according to experimental observation [23].…”

Section: Calibration Under Saturated Conditionmentioning

confidence: 99%

“…This class of rocks usually exhibits a selected preferable orientation of distinct bedding planes, which result in inherent anisotropic behavior on the macro-scale. A large body of research [10,[17][18][19][20][21][22][23][24][25][26][27] has been conducted on inherently anisotropic rocks, including experimental characterization, theoretical studies and numerical modeling. Various topics have been covered, including micro-and macro-structural factors in anisotropy and the interactions between inherent and induced anisotropies.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of inherent anisotropic behavior of partially saturated clayey rocks

Zhou

Zhang

et al. 2013

Computers and Geotechnics

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a b s t r a c tClayey rocks are frequently chosen as a geological barrier material for underground repositories. The inherent anisotropic mechanical behavior and the evolution of mechanical behavior with water content are two crucial material properties for the safety analysis of these structures. The present paper focuses on numerical modeling of the inherent anisotropy and the effect of water content, as well as the interactions of these properties in partially saturated clayey rocks with preferably oriented bedding planes. A discrete thermodynamic approach is adopted for describing the inherent anisotropic mechanical behavior, and the anisotropy of the elastic parameters, plastic evolution and damage evolution are considered. Capillary pressure is introduced to describe the effect of the water content with the help of the effective stress concept, and a procedure for the identification of the model parameters is presented. Finally, the proposed model is applied to a study of triaxial compression tests of argillite with different orientations of the bedding planes and variable water content. In summary, the main features of the studied material are well reproduced by the model.

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Laboratory investigation of the mechanical behaviour of Tournemire shale

Cited by 610 publications

References 4 publications

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing

Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing

Description of hydraulic and strength properties of anisotropic geomaterials

Modeling of inherent anisotropic behavior of partially saturated clayey rocks

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