Influence of the loading conditions on the mechanical response of granular materials as constrained from experimental tests on synthetic rock analoguematerial

Nguyen, S.; Chemenda, A.; Ambre, Julien

doi:10.1016/j.ijrmms.2010.09.010

Cited by 40 publications

(37 citation statements)

References 23 publications

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“…Experimental evidence of failure mode transition due to changes in confining pressure has been presented by Paterson (1978), Ramsey and Chester (2004), Bobich (2005) and Rodriguez (2005) based on triaxial experiments on Marble and Sandstone as well as by Chemenda et al (2011) and Nguyen et al (2011) based on pressed TiO 2 powder. These tests showed that with increasing confining pressure the fracture style changes and the angle between the fracture and maximum principle stress direction increases.…”

Section: Introductionmentioning

confidence: 98%

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

Kettermann

Urai

2015

Journal of Structural Geology

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Section: Introductionmentioning

confidence: 98%

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

Kettermann

Urai

2015

Journal of Structural Geology

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“…In any case, the rupture does not follow directly the elastic straining (as is assumed in LEFM) but is preceded and accompanied by an inelastic deformation (for both GRAM1, Figure a, and a hard rock, Figure b) that must be taken into account. In fact, the increase of ductility (reduction of brittleness) with P c is well known from the numerous experimental studies and results in the transition from σ 1 ‐parallel ( ψ ≈ 0) to σ 1 ‐oblique (shear, ψ > 0) fracturing (e.g., Bésuelle et al, ; Fortin et al, ; Nguyen et al, ; Wong et al, ; Wong & Baud, ). The plots in Figure show that this is true even within a narrow range of small P c corresponding to the same fracture orientation (or type), ψ ≈ 0.…”

Section: Introductionmentioning

confidence: 99%

“…Chemenda et al () conducted similar tests on Granular Rock Analogue Material (GRAM1) made of very small bonded TiO 2 grains (Nguyen et al, ). The mechanical properties of this material have been extensively studied (Mas & Chemenda, , ; Nguyen et al, ). It was shown to behave very similarly to hard rocks, showing the same pressure dependence of properties (Figure ) and variation of the dilatancy factor from positive to negative values with P c increase.…”

Section: Introductionmentioning

confidence: 99%

“…Minimum principal stress σ 3 versus confining pressure P c = σ 1 at fracturing/rupture in conventional (axisymmetric, σ 1 = σ 2 ) extension tests of GRAM1 (a) and Berea sandstone (b). Data for sandstone are from Bobich () and for GRAM1 from Nguyen et al () and Chemenda et al (). ψ is the angle between the fracture plane and σ 1 direction;

σ_{t}^{0}

and

σ_{c}^{0}

are the initial tensile and uniaxial compression strengths;

σ_{int}^{0}

is the abscissa of the intersection point of the horizontal and inclined blue lines approximating the experimental data.…”

Section: Introductionmentioning

confidence: 99%

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Origin of Regular Networks of Joints: Experimental Constraints, Theoretical Background, and Numerical Modeling

Chemenda

2019

JGR Solid Earth

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Experimental data show that inelastic straining occurs even at very low pressure before and during brittle fracturing. This process is therefore investigated within the framework of elastoplasticity using 2‐D, three‐layer finite difference modeling. The constitutive model includes both tensile and shear failure mechanisms coupled at the level of the strain softening law. The modeling results show that sets of parallel joints initiate as pure dilation bands, the narrow σ3‐normal bands of localized dilatant damage (inelastic deformation). The band thickness, length, and the initial strain softening degree within it are proportional to the ductility of the material, which increases with the effective stress level (σ1) or pressure. The strength reduction within the bands is accelerated at a certain stage, and the strength locally reaches zero resulting in fracture initiation. The initial fracture then propagates in Mode I following the propagating band. The fracture (joint) appears thus as a band of damaged material with the increased porosity, which is maximum along the axial zone of the band where the material is completely broken. The damage is due to both tensile and shear mechanisms. The role of shear failure increases with the ductility (pressure) increase, which also leads to the band thickness increase. These processes can result in small (band thickness)‐scale oblique shear fractures within the band, causing the increase in the roughness of fracture walls organized in plumose patterns typical of both natural and experimentally generated joints.

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“…With the presented problems in mind, we report in this paper the results from the axisymmetric extension tests on an “ideal” synthetic granular, frictional, cohesive, and dilatant physical rock analogue material GRAM1 [ Nguyen et al , 2011]. We concentrate on this loading configuration because it provides the most direct and easiest way for generation of extension (other terms are tension and tensile) fractures, which are the most frequent in different materials and above all in geological structures, where they are called joints [e.g., Pollard and Aydin , 1988; Mandl , 2005].…”

Section: Introductionmentioning

confidence: 99%

Mode I cracking versus dilatancy banding: Experimental constraints on the mechanisms of extension fracturing

et al. 2011

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Fractures or discontinuities perpendicular to the least stress σ3 were generated in a synthetic rock analogue (granular, frictional, cohesive, and dilatant) material in axisymmetric extension tests. These fractures are of two types defined by the mean stress σ. When σ is very small, the fractures form through the mode I cracking at tensile σ3 equal to the material tensile strength. The fracture walls have smooth surfaces. At higher σ, these surfaces become rougher, with the topography features forming faint or delicate plumose patterns. The amplitude of the plumose topography increases with σ. The axial stress σ3 at fracturing reduces in magnitude and changes in sign with the σ increase. Thus σ3 orthogonal discontinuities can form at compressive σ3. SEM observations show that these discontinuities are deformation localization bands where the material is characterized by the heterogeneous decohesion and volume and porosity increase due to dilatancy. The band thickness is several grain sizes. At formation, the bands are not opened, so they are not mode I fractures. They become fractures with plumose fractography after the separation of the sample parts along the band. The formation mechanism of these discontinuities or fractures is not completely clear, but it is suggested that it represents a running constitutive instability in the form of dilatancy banding (with further σ increase the bands become inclined to σ1, i.e., shear). The similarity between the experimentally generated plumose surface fractures and natural joints is discussed, and it is suggested that they can be formed as propagating constitutive instabilities.

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Influence of the loading conditions on the mechanical response of granular materials as constrained from experimental tests on synthetic rock analoguematerial

Cited by 40 publications

References 23 publications

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

Origin of Regular Networks of Joints: Experimental Constraints, Theoretical Background, and Numerical Modeling

Mode I cracking versus dilatancy banding: Experimental constraints on the mechanisms of extension fracturing

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