Overturning:
Another effect of the horizontal forces is its tendency to overturn the retaining wall about its toe D. The overturning moment is Ph. y¯, where y¯ is the distance of resultant of the horizontal forces above the base.
The stabilizing moment which is caused by the weight of the wall (or any material resting on the slopes of the wall) is given by W ⋅ z¯, where z = (b - x¯) is the distance of the resultant from the toe D.
For the stabilizing moment to be greater than overturning moment, we must have W ⋅ z¯ > Ph⋅ y¯ and the factor of safety against overturning is W ⋅ z¯/ Ph ⋅ y¯ which should not be less than 1.0. Normally the safety factor is taken as 2.0.
FS = W z /Ph y¯
Figure