We have a proposal for services to monitor settlement platforms for an interior excavation and underpinning of a foundation. The elevations need to be measured to 0.005'. I havent done this for many many years, and I was told that all the micrometers in use now are in metric (and, of course there are none available for the levels we have)
Cost estimates range from $4105 for a NA2 Leica level, micrometer and rod, and $6000 for a digital DNA03 - Leica w/rod $6305.00 (converts to ft).
Have any of you done settlement platform monitoring lately, and what techniques/equipment did you use to achieve this desired accuracy?
Thanks
I've only had to monitor settlement on bridge cones and large fill areas. I used a Leica NA3003. I made sure to have two solid BM's on natural ground. One that I ALWAYS started from, and the other as a check. When it came time to shoot things in, the contractor had to stop work. Other than that, do the normal routine; peg test the level, & close your loops.
Check out your local dealer for rentals, no sense in buying if your only going to use the equipment a few times.
Back in circa 1986, monitoring the concrete (while it sets) slab for one of the MetroRail platforms for the WAMATA 'Orange Line'... Anyway, this can be achieved using 'Old-School' techniques such as the "Three Wire" differential leveling methods and staying in the first section of the standard 25' fiberglass rod.
Also, around the same era, monitoring the Smithsonian Institute, same "Three Wire" technique is employed using an invar rod.
While modern technology and instrumentation may expedite results and minimize potential errors..'Old-School' methodologies can still produce expected results.
I have a wild heerburgg NAK 2 with a parallel plate micrometer.
It is in mint condition. Only been used in a machine shop. It is a 40x
And i have the original tripod, mint condition also. I would be interested
in selling it. Think it specs out to. 03 mm per double kilometer
run with invar rods. I have some other goodies that go with it.
Let me know if you are interested.
You can get good results with lesser levels using proper techniques as
one gentlemen pointed out.
Last monitoring i did i used a dini digital level and a Sokkia B2o. I had very similar results.
Digital is the way to go. Setup standardized procedure and naming conventions for your obeservations. Set up solid benchmarks on stable structures outside of the area of disturbance. I would run double loops through the plates as a check too.
How many plates are we talking here? How frequent are the observations to take place? How long of a duration? Depending on the answers to those questions, you can determine the level of programming you want to do in Excel to setup formulas to automate your reports from the digital level output.