Creep behaviour of saturated clay subjected to cyclic loading in plain strain condition

Creep of clayey soils is defined as the time-dependent deformation under sustained stresses, due to viscous behavior of the soil skeletons. Creep behavior of soil depend upon main factors which include time, temperature, soil type, soil structure, stress history, stress state and drainage conditions. In this study, a series of one-dimensional oedometer laboratory creep tests were conducted on samples subjected to cyclic loading in order to study the effect of overconsolidation ratio (OCR) and duration of preloading on the secondary consolidation coefficient of the soft clay. Test results reveal that the secondary consolidation coefficient of theoverconsolidated samples are smaller than that of the normally consolidated samples, and decreases with increasing OCR with a drastic drop for OCR values close to 1. On the basis of the isotache model, an equation for secondary consolidation coefficient compression index is proposed as a function of OCR and duration of preloading. The laboratory tests show that the actual measured secondary consolidation coefficient is independent of time. Therefore, to comply with this reality, the proposed equation was modified to be independent of time and laboratory test results were used to calibrate parameters of the newly proposed equation.