Abstract: Based on the self-made model experimental system of dynamic frozen soil-pile interaction, experiments about dynamic property of model pile foundation under lateral dynamic loads in -5℃, -3℃ and partially thawed permafrost were conducted. This paper mainly studies the displacement-force relationship of pile head, dynamic stiffness of pile foundation in horizontal direction and bending moment distribution of pile body in different permafrost mentioned above. The results show that the dynamic response character of pile foundation and frozen soil temperature is closely related. Pile foundation has a lager lateral stiffness in frozen soil, and the displacement-force curve of pile head presents a reverse S-shaped when the gap between soil and pile interface becomes larger. The dynamic property of pile will improve with the decrease of permafrost temperature; and it will decrease significantly when a thawed layer presences in the top of frozen soil; in this case, dynamic stiffness of pile head will reduced greatly; and the pile could generate a larger lateral displacement under relatively small dynamic load; at the same time, the greatest bending moment of pile is larger and the depth of this moment point is bigger than those of pile in completely frozen soil. Therefore, it should pay more attention to the seismic damages of pile engineering in permafrost zone when a thawed soil layer exists in summer.

Key words: frozen soil, pile foundation, thawed soil, experimental study, lateral dynamic load, pile-soil interaction