Influencing Factors of Bearing Behavior of Settlement Reducing Pile Foundation for Immersed Tunnel

Settlement reducing pile foundation has recently been proposed as an important progress in the design theory of pile foundation, which is one type of deformation-based foundations. Compared with the common design method, settlement reducing pile foundation can greatly reduce the number of required piles. Aimed to the influence of pile cap, cushion, pile spacing, pile length on bearing behavior of settlement reducing pile foundation, the indoor tests on steel pipe settlement reducing pile foundation for immersed tunnel were carried out in sand. Based on uniform design, the six groups of tests with 3×4 pile groups were conducted, furthermore, earth pressure, axial force of pile shaft, and foundation settlement were measured. When the load applied increased, the plastic failure of the soil occurred under the corner of immersed tunnel. The result shows that the earth pressure distribution against immersed tunnel is similar to the normal base reaction in sand which is big in the center and small in the border. The correlation analysis result indicates that apply pile cap, reduce cushion thickness, increase pile spacing and increase pile length can increase the pile load sharing ratio. Compared with the average value of correlation coefficient of each influencing factor, pile length has the most remarkable effect on the pile load sharing ratio, then cushion and pile cap, and pile spacing has the minimal effect among these influencing factors. The research can provide a reference for design of relevant projects.