They are building this rail tunnel, only 180 meters long, under the Macdonald–Cartier Freeway (so called Highway 401). They claim they are using these `innovative techniques`. To me, they are not new techniques. Am I missing something?

"SEM (sequential excavation method): is a modern tunnel design and construction method. Earth, rock and debris are removed steadily at a one-metre pace, with the tunnel divided into sections. Machinery like the ‘scooptram’ front end loader to haul away material five tonnes at a time is used.

Excavation with Shoring: during excavation, the exposed area is immediately supported by spraying a layer of ‘shotcrete’, by a shotcrete robot, after which a reinforced temporary lining called “welded wire fabric”. Then lattice girders are installed as an additional measure.

Canopy tubes: in spring, canopy tubes were installed using auger boring. These tubes are 12-metre-long metal hydraulically pushed by a giant drill under the highway to encase the tunnel. As the augers turn they expel the material they excavate from out of them. These canopy tubes are the solid structure of the tunnel, in order for the passage of the tunnel to be bored through.
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https://bramptonist.com/theres-a-massive-tunnelling-project-going-on-under-the-401/
#canada #ontario