Rubber Jacket Stiffness in triaxial tests

[rdmanchanda]

I need to know approximate values of rubber jacket stiffness (both shear and normal) used in triaxial tests. I have to simulate the triaxial test on PFC and need to model this rubber jacket. I also need a value of the porosity of this rubber jacket.

Can anybody help me in this?

 

[iandig]

There is a correction figure in BS 1377-8:1990 which is used to apply a correction to the undrained shear strength. I don't have a copy of the standard to hand, but have used the following equation based on this figure:
y = -0.0017x2 + 0.1295x + 0.0517
Where x is the axial strain, and y = the membrane correction factor
This is then used to calculate the correction factor, per cell pressure [i.e. per axial strain] before determining the correction for specimen diameter which is as follows
Correction for secimen diameter = (38/diameter of specimen) x (actual membrane thickness/0.2) x membrane correction factor. This equation is used as the figure is based upon a 38mm diameter specimen, with a membrane thickness of 0.2mm
The same latex membranes are also used in permeability tests and as such are deemed to be impermeable. If you need further info, I think it will have to come from the manufacturer.
Hope this helps