The following figure shows a section of an anchored retaining wall embedded into a saturated stiff clay layer. The sand has a unit weight of yt = 18 kN/m, c' = 0 kPa and ' = 34. The clay has a unit weight of yt = 20 kN/m, cu = 80 kPa and ou = 0. A uniform pressure of 40 kPa is applied on the soil surface. The short term stability of the wall is considered in an undrained analysis. Assume it is a free earth anchor wall support. Use the Rankin's theory of lateral earth pressure to determine the active and passive horizontal stresses. You should apply the requirements of AS 4678 and the partial factors of safety method in estimation of soil pressures. Assume the soil is in-situ and use a structural classification factor of n = 1. Calculate the tie-back anchor force. Determine the shortest length at which this tie-back anchor remains unbonded. Sand: Clay: Load: Yt (kN/m) c' (kPa) o' (deg) Yt (kN/m) Cu (kPa) ou (deg) q (kPa) 18 0 34 20 80 0 40 1 3m 1m Water table 1.5m 40 kPa Not to Scale Sand Clay Td