$5\mathrm{.}2$ Three separate direct shear tests are carried out on identical samples of dry sand. The shearbox is

$6060mm$ in plan. The hanger loads, peak forces and ultimate forces measured during the tests are

summarised below:

TABLE K

Determine the Mohr coulomb parameters $({}^{\text{'}},c^{\text{'}})$ for modeling the peak strength of the soil, the

critical state angle of shearing resistance, and the dilation angles in the three tests.