DELINEATING THE CONCRETE-EARTH FILL CONTACT AT THE EDGE OF A LARGE EMBANKMENT DAM BY SINGLE BOREHOLE SEISMIC REFLECTION IMAGING
Bibliographic record
Abstract
Interfaces between earth fill and concrete structures are zones of particular interest for the monitoring of seepage in earthen embankment dams. Operators of the 660 MW Mactaquac hydroelectric generating station, completed in 1967 on the St. John River in New Brunswick, Canada, are taking a proactive approach to monitoring one such contact between their 32 m high embankment dam and the adjacent, sloped concrete wall of the facility's diversion sluiceway. Plans call for distributed temperature sensing and self-potential monitoring instrumentation to be installed in boreholes parallel to the interface. Prior to drilling the monitoring holes, there is a need to confirm the position of the interface as precisely as possible. To that end, a steeply inclined ‘surveying borehole’ was drilled in the concrete at a conservative offset, sub-parallel to the interface and extending to a slant depth of 50 m. Borehole seismic methods were applied after borehole radar proved unable to achieve sufficient range of investigation. Surface to borehole seismic measurements, and full waveform sonic logging revealed that average P and S-wave velocities in the concrete were 4210 and 2470 m/s respectively, varying approximately +/- 10% between concrete lifts. Single-hole seismic reflection surveying was subsequently carried out in a dry borehole to avoid interference from Stoneley waves, using a very broadband, self-clamping seismic tool (Vibrometric PS8R). This novel tool employs a piezoelectric source emitting pseudo-random pulse trains with a nominal bandwidth of 5 – 60 kHz and eight piezoelectric receivers at offsets of 1.1 – 2.2 m. Measurements were taken at 30 cm depth increments, with the tool oriented once to favour reception of P-wave reflections, and a second time to favour the reception of S-wave reflections from the interface. Initial processing efforts, employing CMP stacking together with median-filtering to attenuate direct wave energy that would appear to represent an unknown guided wave travelling in the dry borehole, has revealed a weak, linear S-wave reflection that is offset 1.0 to 3.4 m from the hole and inclined in close agreement with the expected position of the concrete-earth fill interface.
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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".