In Fig. 8.3, the arrows indicate the numerical values of the vertical effective stress (s′ vo) and the
maximum past pressures′ vm for both consolidation tests. Based on the Casagrande construction technique,
the maximum past pressure s′ vm was determined for the two consolidation tests on Orinoco
clay. These two tests have significantly different values of maximum past pressure (2.75 versus
1.35 kg/cm2). The reason for the difference was due to sample disturbance. Test No. 12 (solid circles)
was disturbed during sampling and only had a vane shear strength (TV) of 0.30 tsf (29 kPa), as
compared to the undisturbed specimen (Test No. 18) which had a vane shear strength (TV) of 0.51 tsf
(49 kPa). Thus sample disturbance can significantly lower the value of the maximum past pressure
of saturated cohesive soil