Performance of three GCLs used for covering gold mine tailings for 4 years under field and laboratory exposure conditions
Bibliographic record
Abstract
ABSTRACT: The performance of geosynthetic clay liners (GCLs) above arsenic-rich gold mine tailings was investigated by the construction of a test cover comprised of three GCL products placed above the tailings at an abandoned gold mine in Nova Scotia, Canada. In parallel research, the performance of the three commercially available GCLs was assessed based on a series of laboratory column experiments. Of the three needle-punched GCLs tested, one has untreated Wyoming bentonite and a woven carrier geotextile; the second has a polymer-enhanced Wyoming bentonite and a scrim-reinforced nonwoven carrier geotextile, and the third has a polymer-enhanced Wyoming bentonite and woven carrier geotextile coated by a thin polypropylene geofilm. After 4 years of exposure in the field and laboratory, the bentonite structure of all exhumed GCLs appeared to be well hydrated with no visible cracks provided that the cover soil thickness was ≥ 0.7 m. The GCL with untreated bentonite exhibited the highest reduction in the exchangeable sodium percentage (ESP; decreased to 1–3% in field and 4–29% in laboratory) and swell index (decreased to 7–12 ml/2 g in both field and laboratory tests). Despite this reduction in the swelling capacity, the maximum measured hydraulic conductivity (k) for this GCL was 1 × 10−10 m/s, which is still considered low. The GCLs with polymer-enhanced bentonite experienced less cation exchange (ESP = 10–27% in the field and 17–53% in the laboratory) than the GCL with untreated bentonite. The k values of the GCL with polymer-enhanced bentonite and non-coated carrier geotextile (3.6 × 10−11 to 7.9 × 10−11 m/s in the field and 1.6 × 10−11 to 6.7 × 10−11 m/s in the laboratory) were lower than those measured for the GCL with untreated bentonite. The lowest measured k values (3.6 × 10−12 to 9.4 × 10−12 m/s) were for the GCL with polymer-enhanced bentonite and geofilm coating the carrier geotextile. All three GCLs prevented the migration of arsenic to the overlying cover soil, even when the GCL was resting directly above the tailings without a foundation layer.
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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) | 0.001 | 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 | 0.001 | 0.000 |
| 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".