Abstract: In order to study the bearing characteristics and the reinforcement effect of micro-steel-pipe pile in deep filling area, the stress-strain relationship of the micro-steel-pipe pile, the axial force of pile body and the displacement of pile top under various loads were measured by laboratory test and field test. The elastic modulus of composite section, the load ratio of steel pipe to cement paste, the transfer law of the pile’s axial force and lateral resistance were analyzed. The results show that the steel tube collar effect on the elastic modulus of composite section is small, the measured value is only 1.2 times of the calculated value without considering the collar effect, and the steel-pipe’s internal force in the micro-steel-pipe pile is relatively large, accounting for about 2/3 of the total internal force. The Q-s curve of micro-steel pipe pile is slowly deformed in filling area, and the load shared by end resistance tends to zero, which shows the characteristic of friction pile. The pile has high bearing capacity in the filling area. And the pile is used to reinforce the actual project, and the maximum settlement is up to the limit of the code, which indicates that the reinforcement effect of the micro-steel-pipe pile on the foundation in the deep filling area is fine.

Key words: deep filling area, micro-steel-pipe pile, internal force of pile, settlement deformation, foundation reinforcement