Somebody wants me to stake a point over the end of a tunnel so they can drill down to drop in a cable.?ÿ
I haven??t checked out the site yet but trying to come up with a concept on how to ?ÿachieve this. I heard the entrance is a vertical shaft maybe a manhole thing... I think I can drop in a point on the floor of the tunnel entrance by treating it as a point on line ?ÿbut then what? I think the tunnel is too long for a staff compass plus surrounding magnetic fields might be magnetic. Anybody see a way besides Ground Piercing Radar?
Gyro.?ÿ Years ago I almost bought a military surplus version for shooting LiDAR verification points.
Smoke and mirrors.
The gyro would be the HOT setup, but maybe not in the budget.
Look up "plumbing a shaft," that's how it was done in the [good] old days.
All ya need to 2 HEAVY plumb bobs, 2 buckets of oil, some piano wire, and misc. survey stuff.
Loyal
You can use a sonde with an EML (electromagnetic locator).
Alternatively, you can try drilling upwards. There are techniques to do this.?ÿ
That is exactly how my Mining Engineer friend described it. You do need a reasonably large shaft.
The Weisbach Method. Used it in '79 to transfer control down a shaft at a molybdenum (sp) mine in New
Mexico.
Depending on how deep the shaft is, some plumbing pipe, and cheap laser pointers could be effective. Build it top side, index it, and put it down the shaft.
N
Go to end of tunnel. Drill up to surface. ?ÿDone.
Come on Holy Cow.?ÿ I showed you and a 100 other Kansas surveyors how to do this on a Saturday morning in Pittsburg, KS many years ago.
Remember my little demo in the front of the room with a Wild T-1A and a Wild objective pentaprism.?ÿ It is THE perfect accessory for a job like Daryl's.?ÿ The pentaprism is clamped onto the objective end of the telescope and the counterweight fits over the eyepiece of any old Wild instrument.
I have one that I could "loan" out and Scott Zelenek has one.?ÿ Old timers here may recall some photos that Scott posted using his pentaprism with an old-style Wild T-2 and a split-bubble telescope attachment to plumb the outer steel girders on the Freedom Tower.?ÿ His application was a unique way to use an objective pentaprism.?ÿ The Wild folks designed it to transfer bearings down shafts.?ÿ In addition to the pentaprism, the only other items one needs to transfer a bearing down a shaft are two 4-5 ft. graduated staves (as the Swiss call them).?ÿ The most time consuming part of the work is building a platform at the top of the shaft to set the tripod on that also has openings to see the marks on the staves at the bottom of the shaft.
Otherwise, as mentioned earlier, a gyro can determine the direction of the drift to within 20 to 30 arc-seconds.
?ÿ
How deep is the tunnel?
Why not vacuum excavate?
Was simply reverse engineering the problem, Gene. ?ÿFrequently, our linear thinking tendencies complicate finding solutions.
Was just teasing you HC. ????
My big concerns are how safe is that "tunnel" and confined space issues regarding breathable air. I often go underground, but those occasions are at metal mines that have ventilation systems; at a minimum a vent bag that goes past where I will be.
Don't count on me to volunteer. ?ÿNot my cup of tea. ?ÿWill gladly allow others to do what they enjoy.
Don??t drill up into a sewer pond or septic tank.
