In an undrained triaxial test on a saturated clay, the Poisson’s ratio is
1
\(\frac{{{\sigma _3}}}{{{\sigma _1} + {\sigma _3}\;}}\)
2
\(\frac{{{\sigma _3}}}{{{\sigma _1} - {\sigma _3}}}\)
3
\(\frac{{{\sigma _1} - {\sigma _3}}}{{{\sigma _3}}}\)
4
\(\frac{{{\sigma _1} + {\sigma _3}}}{{{\sigma _3}}}\)