Study On Working Properties Of Composite Foundation With Tapered Rigid Piles

Based on the National Natural Science Fund Project "study on bearing behavior and settlement of characteristics of composite foundation with tapered rigid friction pile (50578169)"and analyzing research status at home and abroad, working properties of composite foundation with tapered piles were investigated deeply and systematically by large scale model test in the laboratory, theoretical and finite element analysis.1)Four sets of composite foundation have been tested in the laboratory, one of composite foundation with five cylindrical piles,three of composite foundation with five tapered rigid piles with different degrees of taper. Then, the author makes a comparative analysis of test results.The test results reveal deformation trend and changing characteristics of pile-soil stress ratio of composite foundation, and load distribution along the pile shaft. Besides,bearing behavior of composite foundation with cylindrical piles are compared with that of composite foundation with tapered piles.2) Based on the shear displacement method,the Mylonakis & Gazetas model for mutual action between pile and soil,and the E.Winkler foundation model were introduced, then the flexible factors for mutual actions between pile and soil,pile and soil,soil and soil were provided. Considering the performance of cushion, an analysis method to pile-soil-cushion mutual action in the composite foundation was deduced. To verify the method reliable,theoretical results are compared with test results.The comparison shows that the method in the paper provides guiding significance for engineering practice of composite foundation with tapered rigid piles.3)Three-dimensional numerical simulation of working properties of the composite foundation with tapered piles with different degrees of taper was carried out by using large-scale finite element analysis software ADINA 8.1.The influence of cushion thickness and modulus,modulus of soil among piles and pile end soil,pile modulus on working properties of composite foundation with tapered piles are further studied.