Correction for rubber membrane in CU triaxial test

[ypyenpham]

Hi,

Everyone can guide to correct for rubber membrane in CU triaxial test. The diameter specimen is 38mm, height to diameter ratio is 2. The thickness rubber membranes is 0.012''. I don't know to choose Young’s modulus suitable value.

Thanks,
YP

 

[Ron]

Use a condom and neglect it.

 

[BigH]

Ron - remember that MIT or Harvard (can't remember which) actually carried out tests on the "best" rubber membranes - back in the early 1970s? Trojans came in first!

 

[Ron]

BigH...I remember it as well. We used them for years. Higher quality and thinner than the "scientific" membranes.

 

[dgillette]

And more versatile!

 

[BigH]

Dave - don't tell me you reuse 'em!! Won't work so well with the end cut off!

 

[dgillette]

Is that why I have 14 kids?





(Really only two.)

 

[Ron]

The lab techs always complain when they have to use the used ones!!

Dave...I thought you would have figured it out after about #10.

 

[GeotechinTraining]

If you're testing very soft or sensitive clays, it can be important.

From my graduate lab class:

Membrane resistance (N) = -pi*initial membrane diameter* thickness * 140 N/cm^2 * (axial strain +0.66*volumetric strain)

Volumetric strain is 0 for undrained shear

 

[ypyenpham]

Hi, GeotechinTraining

Your formula is very good. But this is your experiential lab. Where is the formula refer? Book or paper names?

TY

 

[paganel]

You could check BS1377art 8, there is a short paragraphy about membrane correction.