According to Winkler's assumption [26], the coefficient of subgrade reaction Ks is relevant to itself ([K.sub.S0]), the type of backfill, and the displacement of backfill.

The spring stiffness is equivalent to the coefficient of subgrade reaction [K.sub.S].

According to (29), variation in the coefficient of subgrade reaction [K.sub.S] causes variation in earth pressure [P.sub.i] because [P.sub.i] is a function of Ks.

As mentioned above, damage in the anchoring section can also be simulated by a decrease in additional stiffness, which is relevant to the coefficient of subgrade reaction [K.sub.S].

(1) It is assumed that no external loads or constant loads are applied to the backfill and the wall with the relationship between earth pressure and coefficient of subgrade reaction. However, this method maybe not suitable when the external loads are variable.

The e-lg P curve is a straight line (curve (bc) in Figure 5), and the earth pressure is a function of one variable coefficient of subgrade reaction. Based on the coefficient of the subgrade reaction, the relationships among the alarming index, earth pressure, and damage stability of the retaining walls are analyzed.