The design of structure like retaining wall requires the knowledge of the earth pressure acting on the back of the wall because of the soil backfill in contact with it. The amount of the earth pressure against the wall depends on how the wall moves relative to the soil mass.

When there is no wall movement at all i.e., zero movement tendency of wall then corresponding earth pressure is called earth pressure at rest. When the retaining wall has tendency to move outward from the backfill and it gives expansion of soil mass making the soil as loose and makes failure of the soil. In this condition, the failure wedge moves downward. The pressure acting on wall at this failure condition is known as active earth pressure. Since, wall moves away from the backfill earth pressure decreases and approaches to minimum value. When the wall has tendency to move towards the backfill it compress the soil behind the retaining structure and makes the failure of the soil. In this condition, the failure wedge moves upward due to maximum compressive pressure. The pressure at this plastic failure condition is known as passive earth pressure. The pressure at this plastic failure condition is known as passive earth pressure. Since, the wall pushes against the soil mass and thus higher earth pressure is developed.