Consider a $3-$m$-$high $(H)$ retaining wall with a vertical back and a horizontal granular backfill. Given: $=15\mathrm{.}7k\frac{N}{m^3},{}^{\text{'}}=15,$ and ${}^{\text{'}}=30.$ Estimate the passive force, $P_p,$ by using

a$.$ Coulomb's theory

b$.$ Shields and Tolunay's solution $($method of slices$)$

FIG. $14\mathrm{.}20$ Variation of $K,$ with ${}^{\text{'}}$ and $\frac{{}^{\text{'}}}{{}^{\text{'}}}($Based on Shields and Tolunay's analysi