Stability of dual square tunnels in cohesive-frictional soil subjected to surcharge loading
Bibliographic record
Abstract
The stability of dual square tunnels in cohesive-frictional soils subjected to surcharge loading has been investigated theoretically and numerically assuming plane strain conditions. From the viewpoint of the efficient utilization of underground space for human activities, noncircular openings and tunnels should be preferred in the design stage. Despite the importance of this issue, previous research on the subject is very limited. At present, no generally accepted design or analysis method is available to evaluate the stability of multiple tunnels–openings in cohesive-frictional soils. In the design stage, it is important to consider the interaction effects of dual tunnels. Unlike the case of a single tunnel, the centre-to-centre distance appears as a new parameter that must be considered and plays a key role in tunnel stability. In this study, continuous loading is applied to the ground surface and a smooth interface condition is modelled. For a series of tunnel size-to-depth ratios and material properties, rigorous lower- and upper-bound solutions for the ultimate surcharge loading are obtained by applying finite element limit analysis techniques. For practical suitability, the results are presented in the form of dimensionless stability charts and a table with the actual tunnel stability numbers closely bracketed from above and below. As an additional verification of the solutions, upper-bound rigid-block mechanisms have been developed, and the predicted collapse loads from these mechanisms are compared with those from finite element limit analysis. Finally, a discussion is presented regarding the location of the critical tunnel spacing between dual square tunnels where interaction no longer occurs.
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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 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".