$2\mathrm{.}19$ A consolidated$-$drained triaxial test on a normally consolidated clay yielded the

following results:

All$-$around confining pressure $={}_3=115k\frac{N}{m^2}$

Added axial stress $at$ failure $==230k\frac{N}{m^2}$

Determine the shear stress parameter ${}^{\text{'}}.$