Taking moments of all the forces about M,
f– d (g + d/2) = 0
Substituting the value of = 4c – h in the above equation,
f – (4c – h ) d (g + d/2) = 0
or
where,

g is the distance of the tendon above dredged level,

f is the distance between the point of application of force and tendon (M) = g – .

The above equation can be solved for d.

The actual depth provided is 20 to 40% more than d.

The force in the anchor rod can be calcualted as,

The values of and are determined from the pressure diagrams.

The wall becomes unstable when becomes zero.
4c – h = 0, or
In the above equation, is the stability number. Therefore the wall becomes unstable when stability number = 0.25.