Anisotropic Behaviour of Opalinus Clay Through Consolidated and Drained Triaxial Testing in Saturated Conditions

Favero, Valentina; Ferrari, Alessio; Laloui, Lyesse

doi:10.1007/s00603-017-1398-5

Cited by 60 publications

(47 citation statements)

References 32 publications

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“…Material Ratio. According to the practice of mine filling and the previous research in literature [22][23][24], the main factors affecting the optimization of filling material ratio can be divided into internal and external factors. e internal factors include the pumpability and fluidity of the filling material and the strength and mechanical stability of the filling body.…”

Section: Construction Of Optimization Index System Of Fillingmentioning

confidence: 99%

Experimental Research on Material and Mechanical Properties of Rock‐Like Filling Materials in Disaster Prevention of Underground Engineering

Shi

Chen

Zheng

2021

Advances in Materials Science and Engineering

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Rock-like materials can be used as a filling material to improve the stability of underground engineering substantially. And the optimization of the rock-like material is an effective way to improve the performance of the filling material. Firstly, the AHP-FUZZY comprehensive optimization model was constructed for the complexity and fuzziness of the rock-like filling material ratio optimization. Secondly, according to the mechanical properties of rock-like filling materials under special environment (such as high temperature, high humidity, high stress, and high airtight) in old goaf, mechanical properties of rock-like filling materials were studied with the method of field core and laboratory test, which revealed the variation law of mechanical properties with time, and the regression equation between mechanical parameters and time was established with the method of least squares. Finally, the strength and deformation characteristics of rock-like filling materials were monitored by the monitoring and early warning technology. The results show that the optimal ratio of the rock-like filling materials is “E3”; that is, the cement content is 9%, the ash ratio is 2 : 5, and the mass concentration is 74%. The mass concentration is the main factor that affects the slump of the slurry, and the proportion of fly ash and coal gangue content directly affects the stratification and bleeding rate of the slurry. Reasonably increasing the ash and gangue ratio can significantly improve the workability and water retention of the rock-like filling materials. Also, the amount of composite cementitious material is the main factor that affects the setting time and the strength of the rock-like material. What is more, the special environment in gob is good for each chemical reaction fully in rock-like filling materials and strengthens the gelling property of deformation resisting capability, which can be a benefit for disaster prevention of underground engineering.

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Section: Construction Of Optimization Index System Of Fillingmentioning

confidence: 99%

Experimental Research on Material and Mechanical Properties of Rock‐Like Filling Materials in Disaster Prevention of Underground Engineering

Shi

Chen

Zheng

2021

Advances in Materials Science and Engineering

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“…c In range of typical sandstone values (Detournay & Cheng, 1993). d Typical OPA Shale values, neglecting anisotropy (Favero et al, 2018). e Typical for clay minerals (Vanorio et al, 2003).…”

Section: Modeling Reservoir Stimulationmentioning

confidence: 99%

Reservoir Stimulation's Effect on Depletion‐Induced Seismicity

2018

Self Cite

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Depletion‐induced seismicity can pose a problem in some fluid‐producing subsurface reservoirs, in some cases requiring production rate control in order to limit the seismicity. This study investigates the use of reservoir stimulation to reduce the depletion‐induced seismicity rate. Depletion‐induced stress and pore pressure changes are evaluated in a shale cap rock, sandstone reservoir, and shale underburden system, which contains a horizontal well, all modeled in plane strain conditions. The seismicity rate is then predicted based on an existing seismicity model and is found to be dependent on the direction the well is drilled in with respect to the principal stresses. The case where the reservoir has first been stimulated is compared to the case where stimulation has not been performed (using the same production rates) for normal, reverse, and strike‐slip faulting stress regimes. Seismicity is reduced in the case of reservoir stimulation for both reverse and strike‐slip faulting stress regimes. The seismicity rate is only slightly reduced for the normal faulting stress regime. Stimulation also increases the distance that changes in pore pressure dominate over poroelastic stress changes in the reservoir. Further, it is found that the optimal orientation of a horizontal well, in terms of induced seismicity, is parallel to the minimum principal stress in normal faulting stress regimes and parallel to the maximum principal stress in reverse faulting stress regimes. The orientation of a horizontal well determines where the seismicity is located in a strike‐slip faulting stress regime.

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“…Major effort has been made to study its mechanical and hydromechanical behaviour in laboratory experiments (e.g. Nüesch, 1991;Aristorenas, 1992;Bock, 2010;Amann et al, 2011;Wild et al, 2015Wild et al, , 2018Favero et al, 2018;Giger et al 2018). From a geomechanical point of view, the behaviour of OPA is at the transition from a stiff soil to a weak rock.…”

Section: Introductionmentioning

confidence: 99%

Micro-cracking and incipient shear microstructures at low-strain deformation of Opalinus Clay: Insights from triaxial testing and broad-ion-beam scanning-electron-microscopy (BIB-SEM)

Winhausen

Klaver

Schmatz

et al. 2021

Preprint

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Abstract. A microphysics-based understanding of mechanical and hydraulic processes in clay shales is required for developing advanced constitutive models, which can be extrapolated to long-term deformation. Although many geomechanical laboratory tests have been performed to characterize the bulk mechanical, hydro-mechanical and failure behaviour of Opalinus Clay, important questions remain about microphysics: How do microstructural evolution and deformation mechanisms control the 15 complex rheology over time scales not accessible in the laboratory. In this contribution, Scanning Electron Microscopy (SEM) was used to image microstructures in an Opalinus Clay sample deformed in an unconsolidated-undrained triaxial compression test at 4 MPa confining stress followed by Argon Broad Ion Beam (BIB) polishing. Axial load was applied (sub-) perpendicular to bedding until the specimen failed. The test was terminated at an axial strain of 1.35 %. Volumetric strain measurements showed bulk compaction throughout the compression test. Observations on the cm- to μm-scale showed that deformation 20 localized by forming a network of μm-thick fractures. In BIB-SEM at the grain scale, incipient deformation zones show dilatant inter- and intragranular micro-cracking, granular flow, plastic deformation and bending of phyllosilicate grains, and pore collapse in fossils. Outside these zones, no deformation microstructures were observed indicating localized damage. Thus, microphysics of deformation appear to be controlled by both brittle and ductile processes along preferred orientations. Anastomosing networks of deformation bands develop into the main deformation bands along which the sample fails. 25 Microstructural observations and the stress-strain behaviour were integrated into a deformation model with three different stages of damage accumulation representative for the deformation of the compressed Opalinus Clay sample. Results on the microscale explain how the sample locally dilates while bulk measurement shows compaction, with an inferred major effect on permeability evolution. Comparison with the microstructure of highly strained Opalinus Clay in fault zones shows minor similarity and suggest that during long-term deformation additional solution-precipitation processes operate.

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Anisotropic Behaviour of Opalinus Clay Through Consolidated and Drained Triaxial Testing in Saturated Conditions

Cited by 60 publications

References 32 publications

Experimental Research on Material and Mechanical Properties of Rock‐Like Filling Materials in Disaster Prevention of Underground Engineering

Experimental Research on Material and Mechanical Properties of Rock‐Like Filling Materials in Disaster Prevention of Underground Engineering

Reservoir Stimulation's Effect on Depletion‐Induced Seismicity

Micro-cracking and incipient shear microstructures at low-strain deformation of Opalinus Clay: Insights from triaxial testing and broad-ion-beam scanning-electron-microscopy (BIB-SEM)

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