RE: Estimating the Time Require to Run a Triaxial-CU Test 2

• Jul 25, 2011

1
• #2

BigH

Geotechnical

Dec 1, 2002

6,012

TJ

Is this with or without pore pressure measurements? When I was first in Indonesia, I saw many tests with pwp measurements that were strikingly wrong . . . found out that they testing labs sheared the sample in the same time as it would when doing UU tests or triaxial without pwp measurements (i.e., about 20 minutes). Our lab guy was always about 8 hours per single stage (of course, as digillette will correct me) it depends on the permeability of the sample being tested. 8 hrs vs 20 minutes - obviously the test results were off as the pwp didn't equalize across the sample. When questioned the lad told me it was in his AIT (Asian Institute of Technologoy) handbook - but then I showed him the little paragraph that he, as English was probably his third language, missed which said differently.

 

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• Jul 25, 2011

• Thread starter
• #3

vriak

Geotechnical

Jul 19, 2011

4

US

Big H, thanks for your valuable insight. My tests are with pore pressure measurements. I was thinking its going to take one day for saturation, one day for consolidation and one day for shear. Based on my local experience I am pretty sure my samples are highly plastic clays (we haven't drilled the borings yet, but i think PI will be anywhere from 40 to 50). Please let me know your insight about the number of days for each phase (if my estimates are reasonable???).

Thanks

 

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• Jul 27, 2011

1
• #4

Erdbau

Geotechnical

Jan 19, 2008

86

US

Your estimates are reasonable and maybe a bit conservative. The big factor is how many specimens can you test at once (i.e. how many load frames and how many panels. If you only have one load frame, but multiple panels, you will have several specimens to test, but no load frame to shear them with.

What's your setup? How many pressure panels and how many loading frames? From that you will be able to estimate how many tests per day.

If you only have one panel and one frame, the best you can hope for is one per day (if you're lucky: ONLY if it saturates quickly and you can get all your consolidation before you go home for the night and shear it).

 

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• Jul 27, 2011

• Thread starter
• #5

vriak

Geotechnical

Jul 19, 2011

4

US

Erdbau,
thanks for your insight. I have a master panel and two additional panels connected to master panel. I can saturate one sample using master panel and 6 samples using the other two panels. I also have two geotac pumps to saturate and consolidate samples (these pumps are automated). As for the frames i have two loading frames. Hope this helps.

 

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• Jul 29, 2011

• #6

Erdbau

Geotechnical

Jan 19, 2008

86

US

Sounds like you could get at least two a day, maybe more on average. If you got really crazy, you could even get 4 per day, shearing one specimen at night and starting another in the morning on each frame. It would be a grind, but it's doable. And it's assuming that you can get everything saturated relatively quickly. Leave yourself some time for the equipment breakdowns or problems that will almost surely arising when you are testing 108 specimens.

 

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• Jul 30, 2011

• Thread starter
• #7

vriak

Geotechnical

Jul 19, 2011

4

US

Thanks for your insight Erdbau. I will keep in mind your point about equipment problems. I will update as the project progresses.

Thanks

 

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