We know that The Rankine theory of lateral earth pressures is the most widely used theory to find the lateral pressure which is acting on retaining walls. But this theory has some assumptions which we need to know before hand.
Assumptions in the Rankine Theory of Lateral Earth Pressures
1) The pressure on the back of a vertical wall is the same as the pressure that would exist on a vertical plane in an infinite soil mass.
2) Their is no Friction between the wall and the soil.
What is the Lateral Pressure of Cohesive Soils?
Y=unit weight of soil, lb/ft3 or kg/m3
P=total thrust of soil, lb / linear ft (kg/m) of wall
H= total height of wall, ft (m)
KA= coefficient of active pressure
c= cohesion, lb/ft2or kPa