| Pile-supported foundation consisting of reinforced cushion, pile, pile cap and foundation soil, and it is a new method of soft ground treatment. It is clear that there is a significant load transfer from soil to piles and to substratum due to soil arching and tension of reinforcement so that the total and differential settlements of the embankment are reduced. Simultaneously, the tension of reinforcement can reduce the lateral displacements and improve the stability of the embankment. As the installing of pile caps, the pile-supported foundation, compared with common compound foundation, which is not needed to be closely spaced, and improves the efficiency of the pile strength, and enables the pile-supported foundation a cost-effective method. Because of the above characteristics, the pile-supported foundation has been widely used in soft ground treatment engineering.The working mechanism of pile-supported foundation is complicated, and its theoretical research is lagged behind of its application, so its design theory is not perfect. Consequently, a systemic study on working mechanism of the pile-supported foundation will have theoretical significance and practical value for promoting the progress of design method and construction technology.First of all, a model test was conducted to study on the mechanical behavior and settlement law of the pile-supported foundation under the action of the embankment load. And some influences of the differential settlements between of the piles and soil, the behavior of foundation soil, the size of pile caps and the reinforcements on soil arching and settlement behavior were analyzed in detail.Secondly, the experiments were simulated by using a finite element program and the results of numerical analyses were compared with the model tests. It was emphatically analyzed that the influences of the size of pile caps, the internal friction angle and cohesion of the embankment fill and reinforcements on soil aching effect and the height of soil arching. The results showed that the increasing of the size of pile caps and the internal friction angle and cohesion of embankment fill, and the reinforcements could improve the soil arching effect and reduce the height of soil arching. The height of soil arching and the reasonable range of reinforcement were determined by numerical simulation.Furthermore, an analytical model for the transfer mechanism of embankment load was developed, which considered the influences of the internal friction angle and cohesion of embankment fill, reinforcement, the interaction between piles and foundation soil, the height of embankment and the underlying stratum. And several model tests and projects were calculated by using the analytical model. The results showed that the results from the analytical model are consistent with the actual results from the model tests and the field tests, which verified the analytical model is reasonable. The reasonable range of the internal friction angle and cohesion of embankment fill and the percentage of pile caps coverage was discussed by the analysis on the parameters of a specific project.Finally, by the analysis on the observational data from the two field tests, the variation patterns with the height of embankment were obtained for the settlements, the stresses on piles and soil, pore water pressure, pile-soil stress ratio and load sharing ratio. And the results from the field tests and the analytical model were compared. The results showed that the calculated results based on the analytical model are close to the results from the field tests, which implied the analytical model is reasonable.
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