Investigations on corrosion and mechanical properties of a 20 year old ground anchor exhumed at a power station site
Bibliographic record
Abstract
This paper presents the observed findings and laboratory test results of an anchor exhumed from Manwan Hydropower Station, China, that was installed 20 years ago. The prestressed cables are 25.6 m long with a working load of 1000 kN. It consists of eight strands, and each strand consists of seven wires. The anchor was installed using the “single protection” technique (i.e., the steel strands without greased sheath and were backfilled directly with cement mortar). The anchor was unearthed by excavating a 1.5 m × 1.7 m tunnel. Visual inspection shows that the steel strands in the free and fixed lengths are basically stainless except for a few places where the grout failed to cover the anchor completely, thereby allowing direct contact of the strands with air. The magnitude of rebound of the tendon during the advancement of the tunnel face was simultaneously measured indicating a gradual release of bonding force, which was up to 62% of the prestressed load. This shows that the existence of the bonding force is provided by the bonding between the strand and the grout, while this bonding does not exist in the “double protection” system. The results of the mechanical test confirm that the tensile strengths in all the 33 steel wires exceed the requirement as specified by a current Chinese Standard. The concentrations of various chemicals also satisfy the requirements as specified by the China State Bureau of Quality Technical Supervision. The results of the X-ray diffraction test show that the stains taken from the surface of the strand are composed of FeO and FeOOH, both being oxide products of iron. This shows that exposure of the material to air is an important condition to initiate corrosion. By following the ASTM International G1-03 test procedure, the average corrosion rate is found to be between 3 × 10−4 and 6 × 10−4 mm/year. This investigation generally supports the use of unprotected steel strands in rock anchor.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.000 |
| 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".