Pore Evolution Mechanism in Granite during Ultrasonic Vibration-Assisted Penetration by a Disc Cutter
Bibliographic record
Abstract
The high strength and abrasiveness of hard rock formations are major factors contributing to the slow progress and high costs in tunnel boring machine (TBM) construction. Ultrasonic vibration, by generating stress concentration and fatigue damage through ultrahigh-frequency cyclic impacts, can effectively weaken rock strength and is considered a promising auxiliary technology for TBM applications. This study used nuclear magnetic resonance (NMR) to comparatively analyze the evolution of microscopic damage in granite under composite loading (ultrasonic vibration + static load) versus single loading. The results demonstrate that high-frequency ultrasonic vibration within the composite loading mode induces the microreciprocating motion of mineral particles, which intensifies stress concentration at grain boundaries and microdefects and leads to more pronounced fluctuations in nanopore volume. Furthermore, while the micro-nano pore volume ratio fluctuated under both modes, it exhibited an overall increasing trend with loading cycles. Compared to single loading, the composite mode significantly mitigated the initial decrease in this and amplified the maximum increase degree, indicating that ultrasonic assistance mitigates pore compression while promoting the initiation and accumulation of localized, irreversible microdamage. Under single loading, porosity decreased during the initial cycle due to the closure of primary pores, followed by fluctuating increases in subsequent cycles from new pore generation. Conversely, under a composite loading exceeding 2 kN, ultrasonic vibration prematurely induced damage, causing an immediate porosity increase from the first cycle and a significantly higher overall increase. This is attributed to the efficient promotion of microcrack propagation and coalescence by ultrasonic vibration at lower loads. This study reveals the differential impact of various loading modes on the microscopic damage mechanisms of granite, providing a microscale basis for a deeper understanding of the rock damage process.
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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 | 0.000 | 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) | 0.001 | 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".