Limitations of Rankine's theory : 1. As the retaining walls are usually
constructed of masonary or cement
concrete, the back of the wall is never
smooth and hence frictional forces
develop. 2. On the assumption that wall back is
smooth, the resultant pressure must act
parallel to the surface. 3. The wall back may not always be vertical. 4. The retained soil may not always be cohesionless.