Thread: Ramblings From The USA - 1

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Originally Posted by johnboy

That's what I would have expected; I could have understood that, but these cuttings were excavated back to the shot-holes.
When a hole is blasted, the surrounding rock is fragmented...but these holes were clearly delineated, eighteen to twenty inches apart and twenty to thirty feet deep across the entire face of the cutting.
They'd never been shot...

jb, they may be cutting out the roadway to reduce the incline, leaving the hillside along the shoulder, well off of the road surface. I can show you places down in SW Missouri, NW Arkansas where the road surface passes between shear rock walls forty to fifty feet high, and similar angled bore holes are clearly visible top to bottom. Drill, excavate on one side, then start shearing off the rock in sections. Don't know if they may use small, precision directional shots to speed the process, but I could get the full story with a phone call.

Here's a picture of a deep, terraced cut as an example of what I think you may have seen. Not sure of the location....

roadcut.jpg

Originally Posted by rspears

jb, they may be cutting out the roadway to reduce the incline, leaving the hillside along the shoulder, well off of the road surface. I can show you places down in SW Missouri, NW Arkansas where the road surface passes between shear rock walls forty to fifty feet high, and similar angled bore holes are clearly visible top to bottom. Drill, excavate on one side, then start shearing off the rock in sections. Don't know if they may use small, precision directional shots to speed the process, but I could get the full story with a phone call.

Here's a picture of a deep, terraced cut as an example of what I think you may have seen. Not sure of the location....

Attachment 64389

It's hard to say definitively; but I'm pretty sure you've nailed it Roger.
It appears that the strata is horizontal and the drill holes upandicular, i.e. angled back from the roadway; but straight up and down within that plane.

I'm picking it was done (as you intimated,) so that the excavator operator could shear the face off more accurately; like tearing stamps off a serrated sheet.

It's just I've never seen that done before.

Originally Posted by johnboy

It's hard to say definitively; but I'm pretty sure you've nailed it Roger.
It appears that the strata is horizontal and the drill holes upandicular, i.e. angled back from the roadway; but straight up and down within that plane.

I'm picking it was done (as you intimated,) so that the excavator operator could shear the face off more accurately; like tearing stamps off a serrated sheet.

It's just I've never seen that done before.

It's seen a lot in the US, where they attempt to reduce sharp grade changes on major highways to improve trucking efficiency and allow more consistent speed without overly affecting efficiency. A civil/structural buddy that I worked with for years offered:

My personal thought whenever I see those bore holes is that is what is left behind after the blast. I’ve always assumed the holes were drilled near a free edge and the majority of the force of the blast chose the path of least resistance, leaving a half circle behind. I’ll see if anyone around here has a better answer.

I haven't heard anything more from him.