A Numerical Analysis Of The Vertical Bearing Behavior Of Piled Raft Foundations With Variable Pile Stiffness

Variable pile stiffness piled raft foundation is a new type of pile foundation, but the research on its bearing mechanism is not enough, not having a systematic method for designers. In this paper, a comprehensive analysis of the problem was made.Based on a three dimensional nonlinear numerical model of the coupled finite element-infinite element-interface element, the bearing and deformation mechanism of variable pile stiffness piled raft foundation were analyzed.Duncan-Chang model is used to simulate the constitutive relation of soils; linear elastic model is used to simulate the constitutive relation of piles and the raft; and the Goodman model is adopted in contact plane.The subsoil condition and the depth of the raft have been considered, a comparison among"the same pile lenghth, the same pile space, the same pile diameter"piled raft foundation, long pile-short pile piled raft foundation and stiff pile-flexible pile piled raft foundation has been made.The results of the analysis indicate that long pile-short pile piled raft foundation can geatly reduce raft moment and differential settlement, the load distribution is much more uniform among piles, compared with the traditional design method. In practice, piled raft foundation with stiff long piles in the core area and flexible short piles in the outer area, is economical and practicable.