Triaxial test 1

[GeoMax001]

Hi,

I want to know which type of triaxial is able to withstand the highest strain in a specimen. The specimen is a mix of water, cement and bentonite.

The spec states Strain greater than 6% without cracking, obtained in a triaxial cell at 28 days under a confining pressure of 100 kPa at a strain rate of 0.1 % per minute.

Thanks in advance,

 

[Ron]

My guess is that your material will be too strong for a triaxial cell (could potentially damage your equipment), assuming you have anything more than about 3 or 4 percent cement.
Why not just an unconfined compression test with strain measurements?

 

[GeoPaveTraffic]

It would appear that the spec calls for an unconfined undrained traixal test. As Ron points out the sample may be to strong for soil traixial equipment and you may need to use equipment designed to test rock.

Mike Lambert

 

[Ron]

Good point, Mike....I didn't think about rock triaxial equipment....one of the hazards of working in coastal plains areas!

 

[GeoMax001]

Thank you all for your posts.

I didn't specify the expected strength of the material. The material has very small cement content and the final strength is close to 250 kPa at 28 days.

The specifications request a triaxial test, but it doesn't mention the type of triaxial to be used. The requirement is to achieve 6% strain without cracking while testing in a triaxial. I find this difficult to probe.

How can I probe that the specimen didn't "crack" at 6%?

By visual method?
By Graph of stress vs strain?
By completing a k-test after failure?

What is your opinion?

 

[Ron]

When a crack occurs there will be a "blip" in the stress and/or strain measurement. Usually the load will stop climbing but the strain will increase.

 

[AussieGeoEng]

I find it strange that the onus is on the tester to prevent the sample from cracking. You should be able to complete this test in a standard triaxial (noting a confining pressure of 100 kPa).

Just check the capacity of the load cell. A 5kN load cell is good for up to 2500kPa axial stress.