How to fill up rock-membrane annulus in 170¦C triaxial test?

[RockEater]

Hi,

I want to perform a tempered (~170°C) permeability test in a heatbale triaxial test device.
Problem: The rubber membrane, filter disk plates, load ram, etc... are build for 64 mm diameter samples - my samples, however, have a diameter of 60 mm.
Thus, I have an annulus with a width of 2 mm. Too much to be left open, the membrane creases.

I'm now searching for a method to fill this open space with a material that has a lower permeability than the rock (mudstones), does not affect the consolidation and resists the elevated temperature.

Ideas for now are...
...using a second rubber membrane with a diameter of 60 mm and thickness of 1 mm. However, pushing the rubber-covered sample into the 64 mm rubber membrane will probably be quite complicated.
...wrap around teflon duct tape around the sample, however material consumption will be very high, as this type of tape is usually very thin and samples are 10 to 15 cm long.
...fill up the annulus with some kind of silicone gel, however the membrane can than (most likely) not be reused. Furthermore, if the gel penetrates the sample, the permeability is reduced.
...?

 

[Ron]

Not sure where you are located, but if in the US, Europe or Australia you could do the following:

Use the 60mm membrane, double if necessary, and lubricate with silicone lubricant such as K-Y or similar (cheap and available). Slide lubricated, encased sample into the 64mm membrane...should work.

 

[Erdbau]

A 60-mm membrane will stretch out to 64 mm easily. When you apply cell pressure, the membrane will conform to the sample. The membrane will have to make two right angles (vertical on platen and stone, then horizontal on stone for 2mm (on the annulus) and then vertical against the sample. That's really not asking a lot from the membrane. I would double up on membranes, because I have no idea what happens to latex at 170 deg.C.

Ron's method would work too, but I don't think the lubrication is necessary. This is only a permeability test, right?

 

[RockEater]

Permeability with a little bit of consolidation at the beginning...

 

[Patgeotech]

I agree with Erdbau - there should be no problem stretching the 60mm membrane. We used a metal device, which involved placing the membrane in a metal cylinder and then applying a vacuum (simple bit of suction from mouth) and then releasing over sample. To make the space up (some "undisturbed" samples were not perfect), we added more membranes to take the space up and then applied correction factors. For your permeability tests, this would not apply I supppose. I am also unsure with regards to the temperature/latex apsect.

Can you not get someone to make up a seating platform and head adapters for your 60mm samples?