c$.$ An undisturbed soil sample, $100mm$ in diameter and $200mm$ in height, was tested in a triaxial machine. The sample sheared under an additional axial load of $3\mathrm{.}9kN$ with a vertical deformation of $26mm.$ The failure plane was inclined at $55$ to the horizontal and the cell pressure was $250k\frac{N}{m^2}.$

i$.$ Draw the Mohr circle diagram representing the above stress conditions, and from it determine:

Coulomb's equation for the shear strength of the soil, in terms of total stress;

the magnitude and obliquity of the resultant stress on the failure plane.

ii$.$ A further undisturbed sample of the soil was tested in a shear box under the same drainage conditions as used for the previous test. If the area of the box was $3600m{m}^2$ and the normal load was $1kN,$ what would you expect the failure stress to have been?