Friday, February 5, 2010

Niagara Tunnel 'Grinding' Away

February 4th 2010
The tunnel is 5,757.2 meters long at an elevation below the surface of 89 meters.
There is no tunnel over-break. TBM averaging 18.5 meters per day

The Concrete Invert Bridge is at 3,850 meters

The Restoration Carrier: Grinding is at 1,040 meters
Shotcrete is at 800 meters

Have you ever noticed that nobody else is reporting on this? How can that be? Are they so sick of the toyota-like cover-ups, that they just flee from this? Can everybody sense that they are hiding things?

Anyway the main TBM has it's accelerator stuck and is zooming away full speed. But what else is on the critical path? Yes, the bizarre Restoration Carrier contraption! I believe this concept is new to the tunneling world, and they are going quite slowly. They have been stuck at around 7-800 m for some time now.

And now they have added something new - 'grinding'. What is that? They are grinding away the existing shotcrete? To make the new stuff stick better?

I have a vision of them at this contraption, staring ahead at the major overbreak, and scratching their heads. The previous rock-fall showed a dangerous tendency to 'unzip', much like a fault unzips for an earthquake. Are they actually thinking that this is certain death? Will they take the plunge into unknown waters? I shall wait for the next report.


Anonymous said...

I would like to understand what all that queenston shale below the escarpment cap rock actually looks like. Here in Burlington and Oakville, it seems to be highly weathered when excavated. Does it become more solid as you go deeper and is it more solid under the escarpment where weathering can't get at it? Or are there pockets of clay within the solid shale at great depths? Would the TBM have hit clay seams in the Queenston shale?

Harold Asmis said...

You can see the stratigraphy on the official tunnel site. There are no clay seams, which I have generally found in the first 60m and are due to glacial stresses.

civdis said...

Thanks for the answer. So once you get down about 60m here in Burlington Oakville, you would hit some pretty solid rock. It always seemed strange to me to see these layers of clay then rock in the valleys around Halton. How does glacial stress cause the rock to turn to clay in the upper sections of Queenston Shale.

Harold Asmis said...

Look up Geofish Clarified on the left. Or else look up Rouge River in my archives.