I forgot to mention that test done was Triaxial CU with Pore Pressure. We have all the parameter except the poissons ratio. We dont have any lateral measurment arrangment in the triaxial cell.
Ali

If it were an undrained test, the volume should be constant. Therefore if you have the axial strain, you should be able to compute the coresponding lateral strain to maitain the same volume. It would be approximate, s there would probably be some additional consolidation, and the center will probably strain more than the ends, but you may be able to make a reasonable approximation

You can also use the same method in drained tests, provided that you have precise measurements of volume change during in both consolidation and shearing stages. Konwing the actual volume and the axial deformation you can equate and solve for the diameter and calculate the lateral strain. But the question here is that, in this method you are assuming that the sample is retaining its perfect cylindrical shape after shearing too, which is especially not the case in testing normally consolidated clays in drained condition or overconsolidated clays in undrained condition, also in the case of shearing loose sands in drained conditions. In these cases, bulging of the sample may lead to erroneous calculations. In the case of complete failure by a well observable failure surface, the results may also lead to erroneous evaluations. I suggest that this method of calculation is more reliable when the applied stresses are in the elastic region, or up to the point where the deviator load is equal to 75% of the peak deviator stress.

Eris Uygar