Working Behavior And Failure Mechanism Analysis On Composite Foundation Improved By Rigid Piles With Cap Under Flexible Foundation

With the increasing number of highways and high-speed railways, composite foundation technology is more and more applied to the foundation treatment. Therefore, the research for the stable calculation methods and working behavior in rigid pile composite foundation under embankment load attract more and more attention of engineering circles and scientific community. The existing research paid more attention on cement soil mixing pile and plain concrete pile composite foundation around the embankment slope. As to require the use of highway embankment of reinforced concrete pile and high strength prestressed pipe pile has been widely used in subgrade treatment.In this paper, ABAQUS software is used to establish a 3-D analytical model, which is aimed to analysis the rigid pile with cap composite foundation’s failure under embankment. Previous studies have generally considered that the pile body is linear elastic. And in the analysis, the internal force of the pile is often beyond the limit strength of the concrete and the displacement of the pile is small which cause the result is not safe. By simulating the cracking progress and stress migration during the process of embankment loading with the introduction of Concrete Damage Model which is embedded with rebar layer, the stress and failure characteristics of pile-net composite foundation are studied. Also, the effects of different pile models on the working behavior are compared;Besides, the sensitivity analysis of the influencing of geogrid modulus, soil modulus, pile length and replacement ratio on the settlement of the pile and soil is carried out by orthogonal analysis method. Research has following results. (1) According to the stress state of the pile, the location of the pile can be divided into compression, large eccentric compression, small eccentric compression and stretch bending area. (2) Concrete Damage Model can describe the development of damage and stress transfer of reinforced concrete pile more precisely. (3)Compared with the different pile models, the form of the anti-sliding contribution of the rigid pile with cap and its failure model is related to its position. (4) Sensitivity analysis proves that the replacement ratio of the pile and soil impacts most on the settlement of the pile and soil differences.