Twenty years of FRC tunnel segments practice: lessons learnt and proposed design principles
Bibliographic record
Abstract
The construction of underground infrastructures for both transport purposes (roads, railways, and metro) to face and solve the need of urban mobility but also for mountain, sea straits or rivers crossing and for water transportation (clean or sewage water) has today a relevant role in modern society. In this context, it assumes a particular importance the construction of tunnel linings in a shorter time and in safe conditions to remain within the project budget; full face mechanized tunnels are consequently under considerably improving all over the world with the adoption of bigger and more powerful machines; in this case, the linings are usually made of precast segments. \nParallel to the improvement of mechanized methods of excavation, it is evident the need to also develop the behavior of these tunnel elements in terms of bearing capacity, crack control and water-tightness. To this aim, in the last two decades, Fiber Reinforced Concrete (FRC) was progressively adopted in several tunnel projects. The benefits related to the inclusion of fiber reinforcement in the cementitious composites are several but, the most important, is the noticeable increase of the post-cracking tensile residual properties. Moreover, the fiber reinforcement enables a considerable boost of the tunnel elements production process. The enhancement of the general structural behavior together with the improvement of the industrialization process of tunnel segments are probably the two main key-factors of the continuously growing use of FRC in precast tunnel linings. \nWithin this framework, the aim of this report is to provide advances in the design of FRC tunnel lining in accordance with the objectives of the International Tunnelling Association (ITA) prescribed in Section II of the Statutes of the ITA (ITA, 1976). In fact, even if general standards or recommendations concerning the design of FRC elements are already available, the needed to shed some new light on the specific requirements and loading conditions of tunnel elements is considerable. This document was conceptually agreed during the meeting of ITA Working Group 2 in Budapest, 2009. The first early draft document was presented in Vancouver, 2010. After several discussions and meetings the current version was completed and presented herein.
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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 | 0.002 | 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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.002 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".