Three-dimensional ground settlements and stress-transfer mechanisms due to open-face tunnelling
Bibliographic record
Abstract
A series of three-dimensional, numerical, elastoplastic, coupled-consolidation analyses was conducted to investigate the effects of the stiffness ratio (n = E ′ h /E ′ v ) and the initial coefficient of earth pressure at rest (K 0 ) on ground deformations and stress-transfer mechanisms due to idealized open-face tunnelling (i.e., New Austrian Tunnelling Method or NATM) at a given unsupported length. As n increases, smaller plastic extension strain zones are mobilized at the crown and invert for a given K 0 , leading to a deeper and narrower transverse surface settlement trough. On the other hand, for a given n, the lower the initial K 0 is, the deeper and narrower the computed settlement trough will be. Three-dimensional stress-transfer mechanisms at a tunnel heading are demonstrated through the changes in normal stresses and induced shear stresses around the tunnel. As the tunnel excavation advances, the maximum total normal stress reduction in the lateral direction (Δσ xx ) and in the vertical direction (Δσ zz ) occurs at the tunnel heading, whereas the largest total normal stress reduction in the longitudinal direction (Δσ yy ) takes place at about 0.5D (D = diameter) ahead of the tunnel face. A total stress reduction zone can be identified within 2.0D ahead of the tunnel face, and the stress influence zone diminishes at a distance of about 1.0D beyond the tunnel face. A significant reduction in pore-water pressure, of up to about 75% of its initial value, can be identified around the tunnel heading. Around a tunnel open face, the effective stress coefficient K xz (= σ′ xx /σ′ zz ) and K yz (= σ′ yy /σ′ zz ) rise to approximately 1.8 and more than 2.0 at the crown and invert in the initial K 0 = 1.0 ground conditions, respectively. On the other hand, K xz falls to about 50% of the initial K 0 value at the springline, and the coefficient at the shoulder and heel drops to between 10% and 20%.Key words: open face, tunnelling, NATM, anisotropy, three-dimensional, stress transfer, ground settlements.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".