Bibliographic record
Abstract
This lecture describes the latest findings with respect to the long-term performance of modern municipal solid waste (MSW) landfill barrier systems. Field data relating to the clogging of leachate collection systems and the latest techniques for predicting their performance are examined. It is indicated that the primary leachate collection systems may have service lives that range from less than a decade to more than a century, depending on the design details, waste characteristics and mode of operation. Recent data indicate that landfill liner temperatures can be expected to reach at least 30–40°C for normal landfill operations. With recirculation of leachate the liner temperature increases faster than under normal operating conditions, and may be expected to exceed 40°C. Temperatures (up to 40–60°C) may occur at the base of landfills where there is a significant leachate mound. Temperature is shown to have a significant impact on both contaminant migration and the service life of the liner system. Field measurements and theoretical calculations show that composite liners are substantially better than single liners in terms of controlling leakage from landfills. Also, the leakage rates with a composite liner are very small, and diffusion will dominate as a transport mechanism for contaminants that can readily diffuse through a geomembrane (GM). Composite liners involving a GM over a geosynthetic clay liner (GCL) gave rise to substantially less leakage than those involving a compacted clay liner (CCL). The observed leakage through composite liners can be explained by the holes in, or adjacent to, wrinkles/waves in the GM, and this leakage can be calculated using simple equations. High-density polyethylene (HDPE) GMs provide an excellent diffusive barrier to ions. However, some organic compounds readily diffuse through HDPE GMs, and a combination of GM and an adequate thickness of liner and attenuation layer are required to control impact to negligible levels. The long-term performance of HDPE GMs is discussed. Based on the currently available data, the service life for HDPE GM in MSW landfill is estimated to be about 160 years for a primary liner at 35°C and greater than 600 years for a secondary GM provided it is at a temperature of less than 20°C. Clay liners are susceptible to both shrinkage and cracking during construction (due to heating by solar radiation or freezing) and after placement of the waste (due to temperature gradients generated by the waste). The former can be controlled by quickly covering the liner with a suitable protection layer. The latter can be controlled by appropriate design. The use of numerical models for predicting the service lives of engineered systems and long-term contaminant transport is demonstrated.
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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 | 0.001 | 0.001 |
| 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 | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".