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5 The flow time, Ft, is therefore defined as the time when shear deformation, under constant volume, starts. The flow time is also viewed as the minimum point in the relationship of rate of change of compliance versus loading time. Figures 6 and 7 show typical static creep test plots. Figure 6 shows the total axial strain versus loading time on a log-log scale. The estimation of compliance parameters a and m are obtained from the regression analysis of the linear portion of the curve. Figure 7 shows a plot of the rate of change in com- pliance versus loading time in log-log scale along with the calculated value of the flow time. Figure 4. Permanent deformation parameters and and the flow number. 2.3 FLOW TIME (Ft) Figure 5 shows a typical relationship between the calcu- lated total compliance and time measured in a static creep test. This figure shows that the total compliance can be divided into three major zones: (1) primary, (2) secondary, and (3) tertiary. In the primary zone, the strain rate decreases; Figure 6. Total axial strain vs. time from an actual static in the secondary zone, the creep rate is constant; and in the creep / flow time test. tertiary zone, the creep rate increases. D(t) Secondary Tertiary Flow Time Defines When Shear Deformation Begins Primary time Figure 5. Typical test results between the calculated total Figure 7. Typical plot of the rate of change in compliance compliance and time. vs. loading time.