Durability and sustainability in design and construction of Ontario Line South tunnels
Bibliographic record
Abstract
The Ontario Line South (OLS) is a critical component of Toronto’s expanding rapid transit network, connecting the Ontario Science Centre to Exhibition/Ontario Place. This 5.9 km underground segment includes twin-bored tunnels and seven stations, six of which are below ground. The station construction employs temporary support systems including shotcrete and rock bolts, while permanent structures include reinforced concrete linings and sheet waterproofing membranes. Twin-bored tunnels, constructed using tunnel boring machines (TBMs), feature fiber-reinforced concrete (FRC) precast segments, with waterproofing ensured by segmental gaskets. This paper presents a comprehensive durability evaluation of the OLS underground structures over their 100-year design life, focusing on the impact of ground and groundwater exposure. Durability design follows the Canadian CSA A23.1 (2019) standard and incorporates supplementary full probabilistic service life modeling based on fib Bulletin No. 34 (2006) to validate the prescriptive measures. Using CSA C-1 class concrete with 40% cement replaced by ground granulated blast-furnace slag (GGBS) as a supplementary cementitious material (SCM), the OLS meets its durability and embodied carbon reduction targets, aligning with sustainable infrastructure goals. Monte Carlo simulations show that the final concrete linings achieve a reliability index exceeding the target of 1.3 for up to 150 years, 1.5 times the required service life.
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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 | 0.000 | 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".