Intact Rock Properties of the Rotondo Granite for the PRECODE Project in the BedrettoLab
Bibliographic record
Abstract
ABSTRACT: In order to estimate the depth of the Excavation Damage Zone (EDZ) using empirical or numerical approaches, the key intact properties include the Uniaxial Compressive Strength (UCS), the tensile strength, and the crack initiation threshold. In addition to these test derived values, plotting triaxial test results and determined Crack Initiation values from those tests can help to define Damage Initiation and Spalling Limit failure envelops for numerical modelling of brittle behaviour. In order to predict the extent of the EDZ in the Rotondo granite around a mine-by tunnel being excavated as part of the PRECODE project in the BedrettoLab, Switzerland, a testing program has been conducted. It was found that the static Young's modulus was 52.5 GPa, that the Poisson's ratio was 0.22, that the Direct Tensile Strength reduced from the Brazilian Tensile Strength by a factor of 0.86 was 6.0 MPa and the UCS was 180.9 MPa. In addition, triaxial tests with confinements up to 20 MPa were conducted to determine the intact Hoek-Brown failure envelop, with a mi of 36. These laboratory derived values will be used to predict the EDZ depth and compare it to the measured EDZ from the PRECODE mine-by tunnel in the future. 1. INTRODUCTION Development of brittle damage around underground excavations in highly stressed conditions is a common phenomenon. For deep geological repositories, interest in brittle damage studies began in mid-1980's (Kelsall et al. 1984) with a focus on determining the changes in permeability due to blasting. Much research has since been conducted on various topics related to the development of Excavation Damage Zones (EDZ) for nuclear waste repositories (see Alcaino-Olivares et al. 2024 for details). However, only until more recently has the focus in rock mechanics turned back to time-dependent behaviour of brittle rocks with a related focus on the long-term behaviour of deep geological repositories. Time-dependent brittle fracturing may lead to an interconnected fracture network that could enhance and, in the framework of nuclear waste disposal, may provide preferential pathways for radionuclide migration. Therefore, a comprehensive understanding of brittle fracturing requires a spatial and temporal characterization of the EDZ. A crucial input into characterizing the EDZ are the intact rock mechanical properties, in particular the Crack Initiation (CI) value which has been shown to be a useful intact rock parameter to determine the depth of brittle failure around excavations (Diederichs 2007). This study examines preliminary rock testing results for input into the characterization of the Rotondo granite for the PRECODE project at the BedrettoLab in Switzerland.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".