Abstract: A series of cyclic triaxial tests is conducted by GDS apparatus to investigate the effects of confining pressure, loading frequency, consolidation stress ratio on the hysteretic curves of the remolded weak expansive soil under multi-step loadings and single-step loadings respectively. Morphological characteristics of hysteretic curves are quantitatively described by three parameters, namely, the area S of the hysteretic curve, the slope of curve k, center offset distance d of adjacent hysteretic curves, and the degree of closure εp. The results show that the S, d and εp of the hysteretic curve of weak expansive soils increase nonlinearly with the increase of dynamic stress amplitude, while decrease with the increase of confining pressure, frequency and consolidation stress ratio. The k decreases logarithmically with the increase of dynamic stress amplitude, and increases with the increase of confining pressure, loading frequency and consolidation stress ratio. Hysteretic curves of weak expansive soil are approximately parallel under single-step loading. The parameters of εp, d and S decrease nonlinearly with the increase of loading cycle, which reflects the phenomenon of cyclic creep. The multi-step loading history has a slight influence on the hysteretic curve of weak expansive soil.

Key words: expansive soil, cyclic loading, consolidation stress ratio, hysteretic curve, cyclic creep