The peat soil is a special soil which has obvious regional characteristics. A series of staged cyclic loading triaxial tests is performed to investigate the dynamic deformation properties of the peat soil in Kunming under the conditions of different confining pressures

different consolidation ratios

and different loading frequencies. The effects of confining pressure

consolidation ratio

and loading frequency on the deformation properties of the peat soil subjected to cyclic loading are evaluated through analyzing the dynamic backbone curve

stress-strain hysteretic curve and dynamic elastic modulus. Results show that the dynamic strain of peat soil increases nonlinearly with the dynamic stress amplitude

and there exists a critical stress value at the backbone curve. When the dynamic stress amplitude acting on the soil reaches its critical stress value

the strain of peat soils grows rapidly

and then the soil structure is destroyed; the confining pressure has the most significant effect on the dynamic deformation properties of peat soil

followed by the consolidation ratio

loading frequency is the minimum; the effect of consolidation ratio on the dynamic deformation properties of peat soil depends on the value of confining pressure

which is greater under higher confining pressure; the elastic deformation of peat soil decreases as confining pressure and consolidation ratio increase

while increases as loading frequency decrease

at the same loading level; the stiffness of peat soil decays as loading cycles and loading level increase

the plastic deformation appears and cumulatively grows up; the larger plastic deformation is observed in peat soil with increasing confining pressure and consolidation ratio

decreasing loading frequency.