Influence of carbonate content and micro fabrics on the failure strength of the sandy facies of the Opalinus Clay from Mont Terri (Underground Rock Laboratory)

Kaufhold, Annette; Gräsle, Werner; Plischke, I.; Dohrmann, R.; Siegesmund, Siegfried

doi:10.1016/j.enggeo.2013.01.014

Cited by 26 publications

(18 citation statements)

References 4 publications

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“…The X‐ray diffraction (XRD) analysis (Figure ) of both the Green River and Opalinus shales show that Green River shale is carbonate rich and is assumed to be more brittle while the Opalinus shale is clay dominated and shows ductile macroswelling behavior during excavation [ Bossart et al ., ]. Due to the inhomogeneity of the shale samples from the sedimentation processes, mineral phase contents of these shale samples are variously reported [ Wenk et al ., ; Kaufhold et al ., ].…”

Section: Experimental Methodsmentioning

confidence: 99%

Frictional stability‐permeability relationships for fractures in shales

et al. 2017

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There is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO2 sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction‐stability‐permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate‐rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate‐rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction‐stability‐permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.

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Section: Experimental Methodsmentioning

confidence: 99%

Frictional stability‐permeability relationships for fractures in shales

et al. 2017

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“…Further applications may include the prediction of various rock mechanical and petrophysical parameters that are strongly influenced by lithological and (micro)fabric variations, such as failure strength (e.g. Kaufhold et al 2013), micro-porosity (e.g. Houben et al 2014) or anisotropic diffusion (e.g.…”

Section: Rock-eval Pyrolysis Datamentioning

confidence: 99%

Multi-proxy facies analysis of the Opalinus Clay and depositional implications (Mont Terri rock laboratory, Switzerland)

Lauper

Jaeggi²,

Deplazes

et al. 2018

Swiss J Geosci

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Located in NW Switzerland, the Mont Terri rock laboratory is a research facility primarily investigating the Opalinus Clay as potential host rock for deep geological disposal of radioactive waste. In the Mont Terri area, this Jurassic shale formation is characterized by three distinctive lithofacies: a shaly facies, a carbonate-rich sandy facies and a sandy facies. However, the lithological variability at dm-to cm-scale is not yet fully understood and a detailed lithofacies characterization is currently lacking. Within the present study, petrographic descriptions at micro-and macro-scale, geophysical core logging (P-wave velocity and gamma-ray density), geochemical core logging (X-ray fluorescence) and organic matter quantification (Rock-Eval pyrolysis) were combined on a 27.6 m long Opalinus Clay drillcore comprising the three major lithofacies. The high-resolution investigation of the core resulted into a refinement of the threefold lithofacies classification, and revealed high intra-facies heterogeneity. Five subfacies were defined and linked to distinctive depositional regimes. The studied succession is interpreted as a shallowing-upward trend within a storm-wave-dominated epicontinental sea characterized by relative shallow water depths.

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“…Although instrument-based techniques were used to identify mineralogy, there does not appear to be a clear relationship between mineralogy and durability. This is probably because durability is affected by other factors, such as the microfabric or microscopic texture of the rock (Martínez-Bofill et al 2004;Kaufhold et al 2013;Cano and Tomás 2015). However, it is of greater relevance to note that using this methodology, a particular sample will show a particular PDI value, which allows it to be categorized according to its slaking behaviour, and hence allow its susceptibility to long-term weathering in a slope to be evaluated.…”

Section: Results Analysis and Discussionmentioning

confidence: 99%

“…Resistance to slaking depends on many different parameters, commonly cited in the literature as; permeability, porosity, adsorption, mineralogy, microscopic texture, microfabric, presence of microfractures, etc. (Gamble 1971;Franklin and Chandra 1972;Richardson and Long 1987;Taylor 1988;Dick et al 1994;Dick and Shakoor 1995;Martínez-Bofill et al 2004;Erguler and Ulusay 2009;Kaufhold et al 2013;Gautam and Shakoor 2015;Cano and Tomás 2015). This makes the characterization of slaking behaviour in rocks using a single parameter extremely complex (Erguler and Ulusay 2009;Gautam and Shakoor 2015).…”

Section: Introductionmentioning

confidence: 99%

Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

Cano

Tomás

2016

Rock Mech Rock Eng

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The susceptibility of clay bearing rocks to weathering (erosion and/or differential degradation) is known to influence the stability of heterogeneous slopes. However, not all of these rocks show the same behaviour, as there are considerable differences in the speed and type of weathering observed. As such, it is very important to establish relationships between behaviour quantified in a laboratory environment with that observed in the field. The slake durability test is the laboratory test most commonly used to evaluate the relationship between slaking behaviour and rock durability. However, it has a number of disadvantages; it does not account for changes in shape and size in fragments retained in the 2 mm sieve, nor does its most commonly used index (Id 2) accurately reflect weathering behaviour observed in the field. The main aim of this paper is to propose a simple methodology for characterizing the weathering behaviour of carbonate lithologies that outcrop in heterogeneous rock masses (such as Flysch slopes), for use by practitioners. To this end, the Potential Degradation Index (PDI) is proposed. This is calculated using the fragment size distribution curves taken from material retained in the drum after each cycle of the slake durability test. The number of slaking cycles has also been increased to five. Through laboratory testing of 117 samples of carbonate rocks, extracted from strata in selected slopes, 6 different rock types were established based on their slaking behaviour, and corresponding to the different weathering behaviours observed in the field.

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Influence of carbonate content and micro fabrics on the failure strength of the sandy facies of the Opalinus Clay from Mont Terri (Underground Rock Laboratory)

Cited by 26 publications

References 4 publications

Frictional stability‐permeability relationships for fractures in shales

Frictional stability‐permeability relationships for fractures in shales

Multi-proxy facies analysis of the Opalinus Clay and depositional implications (Mont Terri rock laboratory, Switzerland)

Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

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