Geotechnical instrumentation - Rebar strain gages in Diagram wall

[autanhau]

Dear Expert

I'm new engineer in the Geotechnical Engineering.
Now, i'm a person in charge for Geotechnical Monitoring, and i have to install some equipment on the site for monitoring.
In my project, we have to excavated up do GL -34m. So, we carry out Diagram wall construction with depth GL -44m.
For monitoring in D-wall, we must install Rebar strain gauges for Rebar cage, and we used Rebar Strainmeters (VW) ( Model 4911 · 4911A of Geokon supplier). On the site, we installed by the way:
- Knot the Rebar Strainmeters on the main steel bar on rebar cage.
- Knot the signal cable of Rebar Strainmeters on the main steel, take on the top of D-wall.
- Check for operation of sensor
- Casting concrete with concrete grade C40

My problem:
- After finish casting concrete, we carry out check, take a initial reading. however some sensor only reading for Temperature, do not Strain Reading while after install for rebar cage, sensor well operating.
So, please help me for reason and solution this problem !
Thanks

 

[GeoPaveTraffic]

I am having some trouble understanding your post.

However it sounds like some of the gauges are not working after installation. Unless you are very careful, this can happen. If the gauges are not working, then there is nothing you can do.

I suggest you call Geokon to make sure you are reading the gauges correctly.

Mike Lambert

 

[IRstuff]

HAve you contacted Geokon? What did they say?

TTFN
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Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com:

http://www.engineering.com/AskForum/aff/32.aspx

 

[hokie66]

Just to clarify, I think you mean you are building a diaphragm wall, not "diagram".

Maybe there is no reading because the bars are not being stressed? Or possibly the sensors were damaged while placing the concrete.

 

[autanhau]

Hi everyone !
Actually, before that i used Rebar Strainmeters of ITMSoil suppier. But, it were broken 4/18 sensor,only have temperature reading.
I contacted to supplier and suggested they come to construction site for supporting. They came and directly install Rebar Strainmeters for Panel. After that, after casting concrete 3days, 2 sensor have the same problem on total 6 sensor installed. They said that" Rebar Strain Gauges – 70% of damages are due to poor installation and 30% is due to site condition.
After that, by comment of General consultant, we carried out re-install Rebar Strainmeters inner sonic tube (for sonic test) of the Panel near Panel previous installation (by Geokon supplier).

After this problem, we have to change to using of Geokon supplier.
However, now we continue have a problem with Rebar Strainmeters sensor, broken, no signal. While we very worry and installed carefully. We contact to Geokon and waiting for reply.
And now, we have to Install for compensation, also inner sonic tube.
The question for me " Please compare to value for 2 method ? installing Rebar Strainmeters inner sonic tube and installing for rebar cage.

 

[GeoPaveTraffic]

You need to hire an expert in geotechnical instrumentation. I can't tell from your posts what the problem(s) might be, but your instrument failure rate is way too high. Either the instruments are not being installed properly or the instruments are not the right ones to use for the method of construction being used.

I have installed thousands of instruments, some will fail no matter what you do. The key is to pick the right instrument for the job.

Good luck, hire someone to help you.

Mike Lambert