Effects of geologic time on the initial stiffness of clays

At the same OCR and effective stress level, the natural clay displays an initial stiffness, which on the average, is approximately 50% greater than that of the laboratory resedimented clay. Based on the estimated age of the natural deposit, this corresponds to an increase of the stiffness per log cycle of time of 7%. This value of the aging coefficient, NG, is at the low end of values presented in the literature for clays, which are however all based on shorter aging durations (days to weeks).