Methods of interpretation of borehole falling-head tests performed in compacted clay liners
Bibliographic record
Abstract
The interpretation of falling-head tests in cased boreholes is discussed. These tests are commonly used to measure hydraulic conductivity of compacted clay liners and are often part of the construction quality assurance program. Three methods of interpretation are reviewed with data sets collected from real tests. Two of these methods have been the subject of past research by other authors: the Hvorslev, or time-lag, method and the velocity method. After the limitations of these two approaches have been underlined, a third method is proposed. It uses a best linear unbiased estimator to fit the theoretical head difference function in a plot of falling water column elevation as a function of time (Zt method). The Hvorslev method is found unreliable and is not recommended. The velocity method is theoretically sound, but statistical uncertainty can become high when this method is used in testing materials with low hydraulic conductivity, such as clay liners. Materials with low hydraulic conductivity tend to produce scattered velocity plots, creating considerable uncertainty for the estimated k value. The proposed Zt method is less sensitive to inaccuracies in measurements, yielding a more reproducible result. An interpretation method for stages I and II of two-stage borehole tests is also proposed. This method yields the anisotropy of the liner and the vertical hydraulic conductivity. As a result of inaccuracies in measurements and limited difference between the geometries of stages I and II, the computed anisotropy exhibits significant uncertainty.Key words: clay liners, clay covers, hydraulic conductivity, permeability, in situ test, anisotropy, interpretation.
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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 | 0.002 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".