Tom Wilson, post: 396666, member: 247 wrote: Not going to happen in New England, frost everywhere, very deep some years (4'+) and very little other years. Even if the bottom of the rod is below the frost line the top will be encased in the frost layer and probably will move (up and down mostly). The only things that work are bolts in ledge or the NGS BMs with the bar inside a sleeve, for which you need a big rig drill and lots of $$. You might try one of the Berntsen bars that have an expanding anchor at the bottom, if they are driven below the frost line they may not move, or much anyway.
As far as the rock thing goes, try moving the point a few feet and try again (yes a new set of observations will be required). You can usually tell what you are hitting when you get near, or to, refusal - if the rod continues to move down very slowly it may be a root which, with effort, and a bigger hammer, you can usually get through - if it just gets real hard to pound and the rod doesn't move you are probably on a large rock. I have found that when you hit the giant rocks or ledge there is an abrupt stop to all movement and when you hit the rod you feel the really solid ledge and sometimes you will get a little bounce back or a ringing, but there is no question that you aren't going to go any deeper , get out the hacksaw. You may know all of this but I just thought that I would pass along what I have observed after driving gun barrels, pipes and re bars into New England soil for 50 years.
T.W.
Thank you for this and all the other fine ideas. I love this place for the diversity of opinion (and humor) it provides. As usual, I'll probably use a variety of techniques depending on the point. First, with nearly 30 of these to do, I think most have soil beneath them. There are only one or two very near trees large enough for roots to be a factor (On one, in fact, I USED the root to hold the spike...but that was long ago in my "early days" (Uh, like last year?).
I'm certainly not going to re-set points wholesale as Ken suggested. That's a gargantuan amount of time I don't have. Most of the network has all been adjusted in Starnet already. I'll start with those that are in soil I believe to have some depth...I've checked the State Geologic map and know pretty sure where to expect outright ledge. Those I can drill. The ones in soft dirt I'll set "control points for the control points" and replace with rebar for a higher degree of lateral stability. If some seem tight in very hard soil, I'll just leave as is.
It's not like I'm building a nuclear power plant after all...aside from the learning exercise, and the confidence that I can now achieve FGCC Second Order Class II results for a control network extended via triangulation...once complete it's going to be used for topographic mapping. I have always wanted a battery powered hammer drill so I probably will invoke the "I really need this" statement at the appropriate time.:)
One more thought - I've found a 12" spike sunk down a few tenths and covered survives the frost much better than one that is set flush to the surface. Swing ties and a metal finder help with recovery.
Ken
Ken Salzmann, post: 396706, member: 398 wrote: One more thought - I've found a 12" spike sunk down a few tenths and covered survives the frost much better than one that is set flush to the surface. Swing ties and a metal finder help with recovery.
Ken
No worries there. i can find these blindfolded by now, without a metal detector.
Don't move anything. Set new control from the old control.
Nate The Surveyor, post: 396620, member: 291 wrote: Another idea is to install a COORS station
A COORS station is an ice chest full of Colorado beer; a CORS is a Continuously Operating Reference Station.
rfc, post: 396705, member: 8882 wrote: the confidence that I can now achieve FGCC Second Order Class II results for a control network
Note that the only way to achieve Second Order Class II results is to use Second Order Class II (or better) equipment and procedures. While it's possible to produce results with the same (or better) accuracy using alternative equipment and/or procedures, the only way to conclusively verify that is to exhaustively test against positions known to meet the desired accuracy specification.
It's possible to run 10 miles of levels with a hand level and a stadia board and get First Order closure numbers, but that doesn't make it a First Order level run.
I have always had good luck countersinking the spikes a bit and putting a rock on top of it.
kjypls, post: 396726, member: 9749 wrote: I have always had good luck countersinking the spikes a bit and putting a rock on top of it.
I've been planting little white pin flags next to them as needed. They're only a foot high though, so once the snow gets too deep they're pretty useless. I'll probably just stick a 2' piece of 4" pvc pipe with a cap over those I think I'm going to use actively this winter.
Nate The Surveyor, post: 396620, member: 291 wrote: install a COORS station
[SARCASM]Well, a supply of COORS brew might make you more relaxed about the whole thing, but a CORS would help more with positioning.[/SARCASM]
Before you do anything. Dial 811 and get the underground utilities located. Driving a bar or drilling through an encased fiber optic will set you back a bit.
Daniel Ralph, post: 396820, member: 8817 wrote: Before you do anything. Dial 811 and get the underground utilities located. Driving a bar or drilling through an encased fiber optic will set you back a bit.
Fiber optics??? I don't think so! Too bad, too. If there was some, I'd dig it up and tap it for some decent internet speed.
Too be sure, tho... 811 is a good idea. Driving a rebar through a gas pipeline that is slightly outside of its designated easement really will shut down a site pretty fast.
rfc, post: 396728, member: 8882 wrote: I've been planting little white pin flags next to them as needed. They're only a foot high though, so once the snow gets too deep they're pretty useless. I'll probably just stick a 2' piece of 4" pvc pipe with a cap over those I think I'm going to use actively this winter.
A good sized rock will help with freeze thaw movement.
Jon Collins, post: 396579, member: 11135 wrote: Spikes move real easy in winter. Cordless hammer drills are next to useless. I use a bosch sds max Drill with a honda 2k generator.
I will have to strongly disagree with you on this one. The Bosch 36V SDS-plus cordless cuts trough everything I've come across, granite, basalt and high strength concrete.
John Putnam, post: 396885, member: 1188 wrote: I will have to strongly disagree with you on this one. The Bosch 36V SDS-plus cordless cuts trough everything I've come across, granite, basalt and high strength concrete.
Fair enough. I still have an 18v nicad and it won't do much.
I say leave them. I recover 12" spikes in NH all the time, some dating back to late 80's. In undisturbed areas distance checks between spikes under 0.02' is not unusual. (I would think even with tie pts on the ground thats beter than your going to get trying to replace them.) Long term Vert. is hit or miss. Often I'll find them sticking up above the ground about 0.1' my go to is to boot them back to grade and a lot of times the vert. checks will be under 0.05'. If your concerned about vert. control maybe drive some of those rebars in some easy to navigate to areas and leave some solid bench marks you can adjust to if needed.
It depends on the soil type and water content rfc. If the soil is sandy and well drained there will be very little movement in your spikes. Leav'em. If the ground is wet and has a high clay content it won't matter what you set, it'll eventually be frost jacked out of the ground or slump. I've seen smooth 30' drive rods driven to point of refusal completely jacked out and laying on the ground. Drill holes in bedrock or large boulders would be fairly stable I would think.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Well, this planet has tendencies, to thwart perfection.
N
Kent McMillan, post: 396616, member: 3 wrote: BTW, I forgot to mention it, but I don't think that rebar will resist frost heave as well as a smooth bar would. It's entirely possible I'm wrong about that detail, but it seems to me that the top part of the ground would freeze first and that, grabbing the deformations on the bar, the upper frozen layer would tend to pull the bar out of the ground. The New Englanders would have a better idea about whether that is a mechanism to deal with or not.
More than entirely possible Kent, that is the purpose of the deformations in rebar when used in reinforced concrete. The deformations, or ribs, are for the concrete to grip to the rebar. Transfer that theory to rebar set in ground (as a marker) prone to freeze and you get a substantial vertical problem after sub freezing conditions. In Maryland, we have seen over a tenth of a foot uplift on some markers, sometimes there can be a smaller horizontal component as well. Having said that, consider using a smooth bar or pipe that will resist frost heave. Make a pvc grease sleeve for the top foot or so (look this up elsewhere, or in previous posts). NGS, I believe, published sketches on deep driven rods and sleeves.
In my day to day, practical applications, I like to use crosscuts on concrete curbs. I feel they have permanence and stability better than a rod and cap. Your mileage may vary.
If you want to really use something substantial, there is Berntsen and other catalogs for manufactured markers.