Three-dimensional centrifuge modelling of basement excavation effects on an existing tunnel in dry sand
Bibliographic record
Abstract
Basement excavation may induce unsymmetrical and highly skewed loadings and (or) stress changes in an existing tunnel, not only in the transverse, but also in the longitudinal direction of the tunnel. Although basement–tunnel interaction has attracted intense academic interest recently, it is often simply treated as a plane strain problem. In this study, however, based on a dimensional analysis of the governing parameters, two three-dimensional centrifuge tests were designed and carried out in dry sand to investigate the effects of a basement excavation on an existing tunnel located in two horizontal offsets in relation to the basement. In addition, a preliminary three-dimensional numerical analysis was conducted to back-analyse the centrifuge test and to investigate the effects of the tunnel cover-to-diameter and unloading ratios on the existing tunnel. For the specific conditions simulated and soil type tested, a maximum heave of about 0.07% of the final depth of the basement excavation (He) was induced in the tunnel that ran parallel to and beneath the basement. On the contrary, a maximum settlement of 0.014% Hewas induced in the tunnel located at the side of the basement. For the former tunnel, the influence zone by the basement excavation on vertical tunnel displacement along the longitudinal direction was 1.2L (basement length). By inspecting the measured strains in the longitudinal direction of the existing tunnel, it was found that the inflection point, where the shear force is at a maximum, was located at 0.8L away from the basement centre. Due to stress relief from the basement excavation, the tunnel located directly beneath the basement was vertically elongated, but the one that lay at the side of the basement was distorted. A preliminary numerical parametric study found that tunnel heave decreased as the cover-to-diameter ratio increased, but at a reduced rate.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".