Abstract：The hysteresis curve is the core of building the dynamic constitutive model of soil. The evolution law of hysteresis curve was studied under different confining pressure，loading frequency and dynamic stress amplitude by GDS dynamic triaxial test. The defined parameters，i.e.，the gradient k of the long axis，the area S of hysteretic curves，the ratio ? of the long axis to the short axis of the hysteresis curve and the plastic deformation ，were applied to analysis the hysteresis curve quantitatively. The results show that：the hysteresis curve of expansive soil is narrow and oblique，and k decreases with increasing dynamic strain，and increases with increasing confining pressure and loading frequency. The low frequency loading has less effect on the value of k，S and increase little in the early stage of the development of dynamic strain and increase exponentially later. The influence of confining pressure on S， is in the range of ，while the influence of frequency on S， is in the range of and respectively. There is a clear turning point in the relationship curve between ? and dynamic strain，which firstly decreased and then increased，and the value of ? decreases with the increasing confining pressure and frequency. Compared with the unmodified soil，k of the modified soil decrease while S，?， increase. The stiffness and the expansion of soil were reduced by improving the soil with sand，which has the advantage of reducing vibration when the modified soil was used as subgrade.
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2019, Vol. 38 
