Influence of sand density and retaining wall stiffness on three-dimensional responses of tunnel to basement excavation
Bibliographic record
Abstract
Basement excavation inevitably causes stress changes in the ground, leading to soil movements that may affect the serviceability and safety of adjacent tunnels. Despite paying much attention to the basement–tunnel interaction, previous research has mainly focused on the influence of tunnel location in relation to the basement, tunnel stiffness, and excavation geometry. The effects of sand density and basement wall stiffness on nearby tunnels due to excavation, however, have so far been neglected. A series of three-dimensional centrifuge tests were thus carried out in this study to investigate these effects on the complex basement–tunnel interaction. Moreover, three-dimensional numerical analyses and a parametric study by adopting a hypoplastic sand model were conducted to improve the fundamental understanding of this complex problem, and calculation charts were developed as a design tool. When the basement was constructed directly above the existing tunnel, excavation-induced heave and strain were more sensitive to a change in soil density in the transverse direction than that in the longitudinal direction of the tunnel. Because a looser sand possesses smaller soil stiffness around the tunnel, the maximum tunnel elongation and transverse tensile strain increased by more than 20% as the relative sand density decreased by 25%. Moreover, the tensile strain induced along the longitudinal direction was insensitive to the stiffness of the retaining wall, but the tensile strain induced along the transverse direction was significantly reduced by a stiff wall. When the basement was constructed at the side of the existing tunnel, the use of a diaphragm wall reduced the maximum settlements and tensile strains induced in the tunnel by up to 22% and 58%, respectively, compared with the use of a sheet pile wall. Under the same soil density and wall stiffness, excavation-induced maximum movement and tensile strains in the tunnel located at a side of the basement were about 30% of the measured values in the tunnel located directly beneath the basement centre.
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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 | 0.000 | 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".