Assessment of a Rockburst in the Shaft Pillar of Cooke 4 Gold Mine, South Africa
Bibliographic record
Abstract
ABSTRACT Rockbursts are the most serious and least understood hazard associated with deep underground excavations, typically involving violent energy release and the sudden ejection of rock fragments that may result in fatalities and damage to underground infrastructure. A ML2.8 seismic event with a source dimension of between 110 and 240 m affected two primary working levels at a depth of 1808 m (the 38 and 38A levels). The peak particle velocity (PPV) is generally used to estimate the likelihood of damage to the rock mass and structures. It is not an accurate measure of the PPV generated by a seismic event (particularly in the near field). Still, it represents a scaled-distance relationship, which can be correlated to the rockburst damage. The most severe rockburst damages were encountered on Level 38 of the cross-cut south, consisting mainly of sidewall and hanging wall ejections of rock and footwall heave. The damage extended over a 70-m length of the 38 cross-cut south. From the underground observations, it is estimated that the seismic event's hypocenter is located near the 38 cross-cut south, resulting in this excavation experiencing strong ground motion. Scattered falls of ground were experienced up to 70 m radially out from the hypocenter location. INTRODUCTION Cooke 4 Mine (previously known as Ezulwini Mine), operated by the Sibanye-Stillwater Group, is situated in the Witwatersrand Basin (Fig. 1), which is famous for hosting one of the world's largest gold deposits. Historically, Cooke 4 exploited the Ventersdorp Contact Reef (VCR) of the Venterspost Formation. The rock mass surrounding the stopes, tunnels and shaft consists of quartzites, pebbly quartzites, argillaceous quartzites, the VCR conglomerate, and medium-strong and weak volcanic rocks of the Klipriviersberg Group. The mine ceased to exploit the VCR due to difficulties supporting the weak hangingwall, a 20-m-thick zone of soft ultramafic lavas (48–138 MPa) of the Westonaria Formation (Harvey et al. (2006)). The mine was closed in 2001 and reopened in 2010 to exploit a secondary orebody, known locally as the Upper Elsburg Reefs, in the shaft pillar located 1-1.2 km below the surface.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".