Abstract: To investigate the influence of wetting-drying cycles in seasonal variation on the long-term performance of red clay, the traditional sample preparation method is improved, and the moisture content variation of compacted soil during wetting-drying cycles is controlled in the regime of saturation from the optimum water content to full saturation. Considering the dripping humidification, the 2% and 4% water content samples experienced by the wetting-drying cycles were prepared. The consolidated drained triaxial shear test and compression test were conducted to analyze the effects of wetting-drying cycles and moisture change amplitude on the engineering properties of compacted red clay. The results show that cohesion c and internal friction angle decrease with increasing cycle number N, and the decrease is significant in the first wetting-drying cycle and then becomes stable. However, the rate of decrease of is less than that of c, and the decrease of shear strength under low confining pressure is more drastic than that under high confining pressure during the cyclic wetting-drying process. Compression modulus E1-2 also decreased with increasing N and the decrease rate is less than that of c but larger than that of . Similarly, c and E1-2 decrease slightly with increasing moisture change amplitude of the cyclic wetting-drying compacted red clay samples. At the moisture content in range of 4%, the compacted red clay shows relatively stable mechanical behavior. It is suggested that the red clay should not be directly used as the backfill material, but can be used as the backfill material of the embankment core, if the drainage and slope protection measures are taken effectively.

Key words: red clay, wetting-drying cycles, moisture content, strength, compression modulus