Any suggestions on how to set an alignment for a TBM 25 metres down a shaft? I need two points at the bottom for the alignment but can not see down into the hole. The dimensions of the hole are 3 metres wide by 6 metres long (usable space at the bottom). the bore is 300 metres long so any error in the setout of the points at the bottom will make a great big ops at the end.
You need to be a member of Land Surveyors United - Surveying Education Community to add thoughts!
Add Posts, Surveying Photos, Videos and Articles to the Surveyor Community
Add Stuff to Community
We are committed to allowing freedom of expression for all of our members, and that includes maintaining a safe space for people with opposing views to express themselves. We get posts from all over the country and even the globe, so needless to say, people come with different viewpoints on lad surveying practices and processes. We see this diversity and variety as a real strength-- dialogue and debate are an integral part of the educational process, as well as an important tool in exploring different sides of complex issues.
Replies
http://www.moussystems.nl/nl/producten/lasers.html
A product from The Netherlands, It can made a verticaal laser-line.
the better way for me is rent a laser proyector to transport a coordinates vertically to the bottom of the shsft, and a giroscopic theodolite to transport your azimuth from the surface.
This is what I would do:
If you can, set up four or five retro targets around the top of the shaft and resect to all of them (using a 90 degree eyepiece - maybe rent one because they're pricey). You might need someone to hold up a target perpendicular to each so you're not looking at them on too oblique an angle. Then just use ref line. As the tunnel progresses always set up in the same place and do the same resection, you shouldn't be too far out. Don't expect to be spot on with any method, as you know, an error of even 0.5mm in your line will make you 150mm out at the end. And your resection from the original control is unlikely to be without error. This is not a good construction methodology if your looking for perfection. Hopefully the tunnel diameter has allowed for some error.
Well, it's VERY old school, but also very precise. We used piano wire for a plumb-bob string (actually used 6 lbs of lead) lowered into 55-gal. drums filled with oil. (Could use smaller barrels) Determine a precise position on the tops of the plumb wires, go into the tunnel and line the instrument on the bottom wires. Voila! I'm sure you can figure out the rest.
(sometimes the "old Pharts" still know a thing or two.
This method is tested for accuracy and practical. No need for sophisticated tools.
If you dont want to invest more a heavy plumb bob should do the trick....but then it has to be suspended and air movement has to be accounted for.... else a plumb line laser should do the job but its costlier.
Tough problem. No idea where to start.
-
1
-
2
of 2 Next