Consider a retaining wall of height $\mathrm{H}$ with a smooth vertical back, retaining a cohesive backfill. The relationship between the major principal stress $\sigma_{1}$ and minor principal stress $\sigma_{3}$ at failure (Plastic equilibrium) can be expressed in the form $$ \sigma_{1}=\sigma_{3}\left(\frac{1+\sin \phi}{1-\sin \phi}\right)+2 c \sqrt{\frac{1+\sin \phi}{1-\sin \phi}} $$ Active State …