From S. B. Tan:
The author has interpreted his results on secondary consolidation by using the empirical approach of Buisman. The writer (Tan, 1971) has suggested that an improved empirical approach would be to plot the ratio of the time to settlement against time in which a straight line would ensue, as shown by the following equation:—
t/δ = Mt + C
in which δ is the total settlement at time t after the dissipation of excess pore water pressure, M and C are empirical constants. The inverse slope 1/M of Equation (1) will yield the ultimate settlement thus overcoming the shortcomings of Buisman's approach in which the settlement does not seem to terminate.
Using the author's results (Fig. 6), the plot of t/δ against t is presented in Fig. 1. It is readily seen that Equation (1) is practically followed except for the first few points when the time is small (i.e. when primary settlement predominates). The ultimate settlement evaluated from the inverse slope 1/M is as follows:—
North Embankment 5.75 feet
South Embankment 3.55 feet
It would appear from the above that the author's estimate of over 6 feet (North Embankment) and over 3 feet (South Embankment) would be the final settlement and this would take place over a period of about ten years.
In Fig. 2, the predicted field settlement/time curve (using Equation (1) and the empirical constants M and C derived from Fig. 1) is shown. It is observed that there is good agreement between the actual and the calculated