Evolution of excavation damaged zones in Opalinus Clay shale inferred from seismic investigations

Williams, M.; Ziegler, Martin; Schennen, Stephan; Loew, Simon

doi:10.1016/j.enggeo.2022.106528

Cited by 16 publications

(5 citation statements)

References 38 publications

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“…(9) to represent the energy dissipation degree at different stress states in the surrounding rock. Eq (10) is the fitting equation.…”

Section: Theoretical Basis Of the Criterion For Dividing Edzs Based O...mentioning

confidence: 99%

“…In practical engineering applications for a specific project, only a set of conventional triaxial tests needs to be carried out, and the empirical formulas for the criterion can be obtained by simple data processing according to the method provided in this paper. In particular, during the numerical simulation calculation, the stress-strain state of any unit in the model is known, and then the value of the energy dissipation degree R Ud of the unit can be calculated by Eq (9) and Eq (10). The dissipation energy in the numerical simulation can be calculated by Eq (8) and Up d = -0.044+0.015σ 3 (Fig 4(F)).…”

Section: Theoretical Basis Of the Criterion For Dividing Edzs Based O...mentioning

confidence: 99%

“…After the fourth stage of excavation is completed, the minimum principal stress and maximum principal strain of all units in the model can be obtained and brought into Eqs ( 9) and (10) to derive the value of R Ud . Based on the four thresholds of R Ud in Table 1, the distribution ranges of the CDZ, HDZ, MDZ and EIZ of the underground caverns can be derived, as shown in Fig 9 . The CDZ is mainly distributed in the area of 0.5~3 m around both the cavern and the connection area of the cavern.…”

Section: Plos Onementioning

confidence: 99%

“…The temporal and spatial evolution of EDZs are characterized by the gradual development of the surrounding rock from a relatively intact state (in situ stress) to a fully adjusted state (new stress equilibrium state after excavation) under the influence of excavation [9]. The formation and expansion of EDZs are the root cause of deformation and the damage of the underground cavity envelope, causing challenges related to stability and seepage, thus impairing the performance and function of the surrounding rock mass [10]. Therefore, it is critical to select reasonable and practical methods to accurately determine the formation mechanism, change trend, and the range of the EDZs of the surrounding rock to provide support for the design of underground cavern support.…”

Section: Introductionmentioning

confidence: 99%

“…To better conduct research on EDZs, many countries or regions have set up specialized underground research laboratories (URLs), such as the URL for the Lac du Bonnet granite in Canada [8,9], the Mont Terri Rock Laboratory for the Opalinus Clay in Switzerland [10,11], the A ¨spo ¨Hard Rock Laboratory for granite in Sweden [12], the URL for the Me ´raillet crystalline rock in the French Alps [13], the Tournemire URL in Francev [14], the Meuse/Haute-Marne URL in France [15][16][17], the High-Activity Disposal Experimental Site in Belgium [18], the Tono mine in Japan [19], the Horonobe URL in Japan [20,21], the KAERI Underground Research Tunnel in Korea [22] and the Jinping URL in China [23,24].…”

Section: Introductionmentioning

confidence: 99%

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The criterion for dividing the surrounding rock EDZs of underground caverns based on the energy dissipation degree

Wang

Zhang

et al. 2023

PLoS ONE

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An energy calculation parameter named the energy dissipation degree (RUd) is introduced based on the analysis of the energy dissipation mechanism and energy evolution characteristics during conventional triaxial tests of the granite of Shuangjiangkou. The deviatoric stress‒strain curve of rock can be divided into five stages using four stress thresholds (crack closure stress σcc, crack initiation stress σci, damage stress σcd and peak stress σp), which also correspond to the four RUd thresholds (RUdc, RUdi, RUdd and RUdp) on the energy dissipation degree–strain curve. A given stress threshold increases with increasing confining pressure; however, a given RUd threshold is basically stable under different confining pressures. Then, a new criterion for dividing the excavation damaged zones (EDZs) in the rock surrounding underground caverns based on the monotonically increasing characteristics of the energy dissipation degree‒axial strain relationship curve is proposed, and it allows for the classification of the surrounding rock into five types of zones through quantitative analysis of the RUd thresholds. Based on the criterion for dividing the EDZs of the surrounding rock mass of the underground cavern, the EDZs of the surrounding rocks of the underground cavern group of the Shuangjiangkou Hydropower Station are analyzed. The distribution characteristics of the EDZs of the rock surrounding underground caverns obtained by numerical simulation calculations based on RUd are basically the same as those obtained by in situ elastic wave tests. However, the RUd-based method for classifying the EDZs of the surrounding rock has the obvious advantage of being able to probe the boundaries of the undamaged zone (UDZ) of the surrounding rock more explicitly, while the method based on wave velocity testing is not sufficiently explicit. The damage zoning of the surrounding rock based on RUd can provide support design advice for the excavation of the surrounding rock, such as the support method, the length of the free section and anchor section of the prestressing anchor, etc.

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“…(9) to represent the energy dissipation degree at different stress states in the surrounding rock. Eq (10) is the fitting equation.…”

Section: Theoretical Basis Of the Criterion For Dividing Edzs Based O...mentioning

confidence: 99%

Section: Theoretical Basis Of the Criterion For Dividing Edzs Based O...mentioning

confidence: 99%

Section: Plos Onementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The criterion for dividing the surrounding rock EDZs of underground caverns based on the energy dissipation degree

Wang

Zhang

et al. 2023

PLoS ONE

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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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Deformation Behavior and Seismic Characteristics of Sandy Facies Opalinus Clay During Triaxial Deformation Under Dry and Wet Conditions

Schuster,

Rybacki,

Bonnelye

et al. 2024

Rock Mech Rock Eng

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Unconsolidated, undrained triaxial deformation tests were performed on sandy facies Opalinus Clay at 50 MPa confining pressure to characterize the effect of water and microfabric orientation on the deformation behavior, mechanical properties, and P-wave velocity evolution. Dry and wet (≈ 8 and > 95% initial water saturation, respectively) samples with 12.6 ± 0.4 vol% porosity were deformed parallel and perpendicular to the bedding direction at a constant strain rate of 5 × 10–6 s−1. Dry samples revealed semi-brittle behavior and exhibited strain localization at failure, while deformation was more ductile at saturated conditions, promoting stable, slow faulting. Peak strength, Young’s modulus, and number of cumulative acoustic emissions decreased significantly for wet samples compared to dry samples; the opposite was observed for Poisson’s ratio. P-wave velocity anisotropy was significantly altered by differential stress, primarily due to the interplay between pore and fracture closure and stress-induced microcrack formation. For samples that were deformed perpendicular to bedding, we observed a reduction and reversal of P-wave velocity anisotropy with increasing differential stress, whereas anisotropy of parallel samples increased. The results suggest that water saturation reduces the pressure at the brittle-ductile transition and that the elastic properties and anisotropy of sandy facies Opalinus Clay can be significantly altered in an anisotropic stress field, e.g., adjacent to fault zones or tunnel excavations. Changes in elastic anisotropy are primarily controlled by the orientation between the pre-existing microfabric and the maximum principal stress direction, stress magnitude, and the degree of water saturation.

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Evolution of excavation damaged zones in Opalinus Clay shale inferred from seismic investigations

Cited by 16 publications

References 38 publications

The criterion for dividing the surrounding rock EDZs of underground caverns based on the energy dissipation degree

The criterion for dividing the surrounding rock EDZs of underground caverns based on the energy dissipation degree

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

Deformation Behavior and Seismic Characteristics of Sandy Facies Opalinus Clay During Triaxial Deformation Under Dry and Wet Conditions

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