Figure 8.6 shows the state of a sample of soil initially normally consolidated at
R0 where the stress p0= pm moving directly to R1 where the stress is same, by
creep or vibration. From the definition of overconsolidation ratio in Eq. (8.6) the
overconsolidation ratios at R0 and R1 are both the same and are equal to 1.0 since
the stresses have not changed. This means that the overconsolidation ratio defined in
Eq. (8.6) does not properly describe the current state of a soil.
where p0 is the current stress and py is the yield stress which is the stress at the intersection of the swelling line through R1 with the NCL. Notice that as the state moves from R1 to R2 in Fig. 8.6, either by loading, yielding and unloading or by creep or vibration the yield stress ratio increases because the yield stress increases from p
y1 to py2.