Hydro-Mechanical Effects and Cracking in Opalinus Clay

Cajuhi, Tuanny; Haghighat, Nima; Maßmann, Jobst; Mollaali, Mostafa; Sattari, Amir; Ziaei-Rad, Vahid; Ziefle, Gesa; Nagel, Thomas; Wuttke, Frank; Yoshioka, Keita

doi:10.1007/978-3-031-26493-1_2

Cited by 3 publications

(5 citation statements)

References 49 publications

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“…The present study and implementation were carried out in the context of the joint research project "Geomechanical integrity of host and barrier rocks -experiment, modeling, and analysis of discontinuities (GeomInt2)" (36). The reader is referred to (15) (in [36]) for an overview of general aspects regarding hydro-mechanical and cracking effects in Opalinus Clay at laboratory and field scales. Regarding the aforementioned references, examples of crack pattern formation in a three-dimensional setting were investigated with respect to their mechanical boundary conditions.…”

Section: Aims and Outlinementioning

confidence: 99%

“…This framework has also been applied in three-dimensional setting (15). In this test case, we demonstrate the influence of a mechanical wall restraint on the cracking pattern, motivated by uncertain boundary conditions in the in-situ setting.…”

Section: Strain Energy Increase and Crack Responsementioning

confidence: 99%

“…These established theories have been applied in different contexts and materials (17,25,52,55,57,86) and have been validated against experimental data at the laboratory scale (14). To account for cracking, poromechanical approaches can be combined with discrete and continuous crack-modeling frameworks (15,17,19,27,32,49,58,73).…”

Section: Introductionmentioning

confidence: 99%

“…Figure15 shows the first realization. The locations of the cracks from this and further realizations are shown in Figure12.…”

mentioning

confidence: 99%

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Modeling Desiccation Cracks in Opalinus Clay at Field Scale with the Phase-Field Approach

Cajuhi,

Ziefle,

Maßmann

et al. 2024

InterPore J

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Geological materials such as Opalinus Clay show complex coupled hydro-mechanical behavior at laboratory and field scales. In the context of radioactive waste disposal, in-situ excavations might remain open for ventilation and operation for decades and, consequently, be susceptible to environmental changes such as desaturation. The saturation changes can then lead to mechanical deformation and desiccation cracks. To account for desiccation cracking at field scale, this study proposes an unsaturated hydro-mechanical model combined with the phase-field approach. Using laboratory and in-situ experimental data as input in the numerical model, the modeling framework is applied for simulating the hydro-mechanical effects and desiccation cracks reported in the Cyclic Deformation (CD-A) experiment carried out in the Opalinus Clay formation at the Mont Terri Rock Laboratory in Switzerland. Simulations with homogeneous and heterogeneous material properties generated from experimentally obtained ranges are carried out. Crack initiation and propagation show a good correlation with the monitored relative humidity range of the experiment. Practical information is summarized to motivate the application of the proposed formulation at different setups. Finally, possibilities to improve the framework and to reason simplification of more abstract models are indicated.

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Section: Aims and Outlinementioning

confidence: 99%

Section: Strain Energy Increase and Crack Responsementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Figure15 shows the first realization. The locations of the cracks from this and further realizations are shown in Figure12.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Modeling Desiccation Cracks in Opalinus Clay at Field Scale with the Phase-Field Approach

Cajuhi,

Ziefle,

Maßmann

et al. 2024

InterPore J

Self Cite

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“…These points are linked with practical examples that pertain to the hydromechanical effects and cracking of the Opalinus Clay. In the Federal Ministry of Education and Research (BMBF)-funded project "Geomechanical integrity of host and barrier rocks -experiment, modeling and analysis of discontinuities (GeomInt2)" (Cajuhi et al, 2023ain Kolditz et al, 2023, these effects have been investigated experimentally and numerically, both at laboratory and at field scales. While interpretation influences the conceptualization of experimental and/or numerical models, a clear goal definition is required to delimit the complex system.…”

mentioning

confidence: 99%

Cross-scale perspective on the Opalinus Clay: insights from the GeomInt2 project

Cajuhi,

Maßmann,

Ziefle

et al. 2023

Saf. Nucl. Waste Disposal

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Abstract. Understanding complex systems, such as radioactive waste repositories, involves the study of cross-scale coupled processes. We discuss some important concepts and their mutual interactions for interpreting such systems based on complementary model-based analyses at various scales (Fig. 1). These points are linked with practical examples that pertain to the hydromechanical effects and cracking of the Opalinus Clay. In the Federal Ministry of Education and Research (BMBF)-funded project “Geomechanical integrity of host and barrier rocks – experiment, modeling and analysis of discontinuities (GeomInt2)” (Cajuhi et al., 2023a in Kolditz et al., 2023), these effects have been investigated experimentally and numerically, both at laboratory and at field scales. While interpretation influences the conceptualization of experimental and/or numerical models, a clear goal definition is required to delimit the complex system. One goal statement in the context of this contribution is to explain the formation of drying cracks, where essential processes and boundary conditions must be pinned down. Monitoring data are critical for determining the correlation between experimental and numerical setups. This is achieved by quantifying and questioning the assignability of information derived from data obtained from core samples tested in the laboratory to field-scale analyses. Numerical modeling can help validate model ideas by reproducing measured data and making predictions beyond the experimentally observable range. The detailed information gained from these studies can be used for interpretation and simplification. In a recent study, we used the phase-field approach to model the formation and evolution of cracks and stated the conditions under which desiccation cracks will develop at the field scale as well as how deep they propagate into the rock (Cajuhi et al., 2023b). This information about the near field can be used to determine how detailed repository far-field models must be and, for example, whether cracks need to be taken into account. Consequently, the cross-scale study of complex systems can lead to more robust analysis results.

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Water Content Evolution in the EDZ of Opalinus Clay: A Methodic Approach for a Comparative Interpretation of Measurements and Modelling

Ziefle,

Cajuhi,

Costabel

et al. 2024

Rock Mech Rock Eng

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In the Mont Terri Rock Laboratory (Switzerland), an interdisciplinary examination program is carried out to increase knowledge about coupled hydro-mechanical effects in Opalinus Clay, which are of significant interest regarding the stability and integrity of a potential storage facility for high-level radioactive waste. This article focuses on the characterization of the claystone in the near field of excavations and related hydraulic effects due to excavation and ventilation. Electrical resistivity tomography (ERT) is applied to characterize the OPA: Several open fractures correlate with regions of high resistivity values, indicating potential preferential flow paths that are relevant for transport processes. Due to the combined interpretation of ERT long-term monitoring and seasonally repeated nuclear magnetic resonance (NMR) measurements, a relationship between electrical resistivity and water content can be established, resulting also in a time-dependent map of the water content around excavations with different climatic conditions. The statistical interpretation of these measurements indicates the existence of small-scale singularities in contrast to dominating, more homogeneous zones. The presented approach leads to a better process understanding of these heterogeneous near field effects and provides a valuable basis for a pragmatic approach to safety assessment.

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Hydro-Mechanical Effects and Cracking in Opalinus Clay

Abstract: In this chapter, we investigate hydro-mechanical effects in the Opalinus Clay, especially those leading to cracking. We present a methodology comprising laboratory and field scale experiments, as well as the development and application of numerical approaches.

Cited by 3 publications

References 49 publications

Modeling Desiccation Cracks in Opalinus Clay at Field Scale with the Phase-Field Approach

Modeling Desiccation Cracks in Opalinus Clay at Field Scale with the Phase-Field Approach

Cross-scale perspective on the Opalinus Clay: insights from the GeomInt2 project

Water Content Evolution in the EDZ of Opalinus Clay: A Methodic Approach for a Comparative Interpretation of Measurements and Modelling

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