$2\mathrm{.}0$

An $8\mathrm{.}5-m$ high retaining wall with a vertical back face retains a homogeneous saturated soft clay. The saturated unit weight of the clay is $19\mathrm{.}6k\frac{N}{m^3}.$ Laboratory tests showed that the undrained shear strength, $c_u,$ of the clay is $22k\frac{N}{m^2}.$

a$.$ Make the necessary calculations and draw the variation of Rankine's active pressure on the wall with depth. $($Note draw the pressure diagram$)$

b$.$ Find the depth up to which tensile crack can occur.

c$.$ Determine the total active force per unit length of the wall before the tensile crack occurs.

d$.$ Determine the total active force per unit length of the wall after the tensile crack occurs. Also find the location of the resultant.