Abstract: With exploiting of the urban underground space, the problem of anti-floating foundation becomes prominent in the soft soil areas. Bored and precast piles are widely used due to their environmental friendliness, but drilling process typically reduces the shaft resistance. Thus a constrained grouting pile is proposed. In order to accurately evaluate the uplift capacity of steel pipe pile with constrained grouting, the failure mechanism is analyzed, and the logarithmic spiral curve is adopted to fit the local slip surface. The simplified calculation formula is derived, and its effectiveness is verified by a classic case study. Based on the design concept of orthogonal experiment, the influencing factors of uplift capacity are compared. The results show that the diameter of pile and the strength of pile-soil interface control the uplift capacity. Field test on the steel pipe pile with constrained grouting is carried out. The test shows that the uplift capacity of the pile is increased by 70%. It is more accurate and safer to use the theoretical formula proposed to calculate the uplift capacity of foundation pile. The research results provide reference for the uplift capacity design of the constrained grouting piles.

Key words: constrained grouting process, steel pipe pile, uplift capacity, logarithmic spiral curve, simplified calculation method