Monitoring

What are you monitoring settlement of? That may change the procedures.

Multistory parking garage going in. Monitoring points on an adjacent building and curb line. I've done this kind of work successfully several other times with other groups. This group only thinks they know how to do it. I need to get some written procedures in place.

Something like this?
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September 13, 2013
Bridge Monitor Survey Field Program

Preamble:

At the request of the , will undertake a monitor survey that involves both ground and structure monitoring. As is the case with all monitor surveys, a tight control network is crucial to the quality of the survey results used to show any deformation that has taken place. Due to the nature of the topography in the area, we envision establishing both an absolute and a relative control network in order to monitor both the ground and structure of the Bridge.

Although we are making a distinction between these 2 levels of control, they will ultimately be tied together into one overall control network. The reason for making the distinction is due to the anticipated movement within the project area and our need to establish control within this area to monitor the bridge structure. The absolute control network will be established with static GNSS observations outside the project area to minimize the chance of disturbance due to ground movement, as shown by Figure 1.

Figure 1: Absolute Control Network

The relative control network will be established within the project area and tied together by conventional and static GNSS survey methods to ensure that it is properly braced. While it is possible that the control points within the project area may shift due to ground movement, they can still be relied upon to show bridge deformation and ground disturbance since the internal integrity of the relative control network will be maintained. The proposed network of relative control points is shown in Figure 2.

Figure 2: Relative Control Network

Proposed Scope of Work:

1) Establish Absolute Control outside the project area using static GNSS methods.
2) Establish Relative Control within the project area and measure in using a mix of conventional ties and static GNSS baselines from the Absolute Control.
3) Occupy each of the relative control points and conventionally measure angles and distances in order to brace the relative control network. Proper conventional ties will be determined once on site and visibility has been accounted for.
4) Monitor the ground using conventional methods, sighting from the relative control points to suitable ground monitor points as determined by and .
5) Monitor and scan the bridge structure using relative control points.
6) Carry out a topographic survey of the surrounding area using GNSS Real-Time-Kinematic (RTK) methods.
This project will require the use of a total station, multiple GNSS Static GPS units, and an ultra-high speed scanner to ensure the integrity of results.
The conventional measurements will be carried out using a total station capable of measuring angles to the nearest second and distances to the nearest two millimetres. The static GNSS observations will be done using up to six GNSS units running simultaneously. The conventional and GNSS observations will be processed using a rigorous least squares adjustment package in order to assess the data and properly weigh and adjust the observations.
Scan measurements will be carried out using a high definition scanner which scans up to 1 million points per second with 3D positional accuracy of 3 millimetres at short range. Scans will be conducted from existing control points within the relative control network with a minimum of 3 additional control points acquired from each scan station. Individual scans will be registered together using the final adjusted control coordinates.

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Note - we've been caught before by our assumption of where the ground is not moving. Slide or settlement areas can be larger than you expect, and you really won't know for sure until you have multiple data sets to check the control network.

That is helpful. Thanks.

Still, I'm looking for something more for crew use. Like using the same instrument and prisms each time. Observing from the same control points each time. Using the same glass each time. Checking tribrachs and rod bubbles. Collimating the instruments before observing. Number of repetitions. Nature of targets. Checks to confirm that the control points being used are stable. Report format.

Many moon ago I did this for a pipe line/fuel depot shooting all the foundations for tanks and above ground piping. I was on the field crew and received 8x10 sheets from my engineer/rls each having a plan view showing the control monument(s) location and all of the locations to be monitored with point numbers. We used the same point number as on the sheet, same control, but sometimes different instruments. If the bust from the expected value was over a certain tolerance we went back with a level and rod. Great filler work. Steve

Norman Oklahoma, post: 344609, member: 9981 wrote: Multistory parking garage going in. Monitoring points on an adjacent building and curb line. I've done this kind of work successfully several other times with other groups. This group only thinks they know how to do it. I need to get some written procedures in place.

I have some written guidelines; be advised that they are about 18 years old, so they are based on conventional instrumentation only. They will work well for your scenario. Let me get them scanned and out to you. Kindly send an email address to me.

Thanks. Received your document this morning and it will be quite useful. It deals mostly with the proper placement of the monitoring targets and somewhat with placement of control. It does not detail survey procedures at all. So I'm continuing to hunt for further information, if anyone has something.

Norman Oklahoma, post: 345066, member: 9981 wrote: Thanks. Received your document this morning and it will be quite useful. It deals mostly with the proper placement of the monitoring targets and somewhat with placement of control. It does not detail survey procedures at all. So I'm continuing to hunt for further information, if anyone has something.

If it is monitoring survey procedures that you most want to see, I will draft another set of recommendations very soon. Thank you for the e mail as well.

Did you look at the Corps of Engineers?

http://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-1009.pdf

That's a lot of good stuff. Thanks for that.