Water-induced softening behavior of clay-rich sandstone in Lanzhou Water Supply Project, China
Bibliographic record
Abstract
The strength of clay-rich sandstone decreases significantly when in contact with water due to softening effects. This scenario can pose a severe threat to the stability of water diversion tunnels during construction and operation periods. To address the issues related to water-induced softening in clay-rich sandstone zones in a water diversion tunnel of Lanzhou Water Supply Project, the microscopic and micromechanical variations of rocks due to increasing water content in two different zones i.e. zones A and B, were determined by various testing methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thin section microscopy, micro-indentation test, sonic velocity test, and slake durability test. The microscopic analysis confirms the presence of montmorillonite mineral which is the dominant problematic geomaterial in engineering application. The integrity and durability of clay-rich sandstone were determined with sonic velocity and slake durability tests to calibrate the results obtained by the micro-indentation test. It shows that the elastic modulus and hardness of clay-rich sandstone decrease with the increase of saturation time, up to 144 h, which is more significant and rapid during early stage of saturation. After 144 h of saturation, the elastic modulus decreases by 89% and 97%, and the hardness decreases by 89% and 99% for zones A and B sandstones, respectively. The results of slake durability and sonic velocity indicate that zone A sandstone remains 56.19% durability after 144 h of saturation, while zone B sandstone loses its durability merely after 72 h of saturation. The clay-rich sandstone starts to dissolve in water when the saturation time exceeds 144 h. The significant decreases in strength and durability of clay-rich sandstone due to water-induced softening are serious threats to tunnel stability. The improvements in the strength of surrounding rock mass by grouting and permeability by installation of drainage galleries can reduce the damage caused by water-induced softening.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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 | 0.000 | 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".