Abstract: 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.

Key words: peaty soil, deformation properties, dynamic triaxial test, backbone curve, hysteretic curve, dynamic elastic modulus