Abstract: In order to investigate the jacking characteristics of continuous penetration of jacked piles in layered soils, a field test is conducted in a pile foundation project in Shanghai to explore the evolution of jacking resistance with penetration depth. Combined with numerical simulation by software ABAQUS, the variation of vertical stress, radial stress and radial displacement of the soil around the pile during the penetration process of jacked pile is clarified. The results show that the softness and hardness of the layered soil govern the magnitude of the jacking resistance. When the pile body is located in the cohesive soil layer, the pile sinking resistance increases slowly or even decreases, and when the pile body is located in the silty clay and sandy silt soil layer, the pile sinking resistance increases faster, and the growth rate can reach 174% in the sandy silt soil layer. The vertical stress and radial stress in the soil around the pile are closely related to the soil properties. The maximum values of the vertical stress and radial stress appear when the pile end penetrates into the clay soil, which are 558.0 kPa and 1 178.0 kPa respectively. When the pile end penetrates into the softer silty clay layer below, the maximum vertical stress and radial stress both deteriorate significantly. The radial stress degradation rate reached 52%. The radial displacement decreases with the increase of radial distance, and its variation regular basically reflects the variation characteristics of soil layer properties.

Key words: jacked pile, field test, pile driving resistance, numerical simulation, vertical stress, radial stress, radial deformation