Three-Dimensional Finite Element Analysis And Optimization Design Of CFG Piles Composite Foundation

CFG pile composite foundation has been widely used in all kinds of soils on which buildings with different structural styles are founded recent years. Tremendous economic and social benefits have been achieved. However, precise theories and design methods are still need to be accomplished. The following aspects are studied in this paper:Firstly, the proper formulas are chosen for the loading capability of CFG pile composite foundation through comparing several typical calculation methods of loading capability and settlement.Secondly, considered the initial geostress and the contact among pile, soil and cushion, a single-pile and nine-pile Composite Foundation model are modeled with the finite element procedure of ANSYS. The major parameters, including the effect of load level, pile length, thickness and elastic module of cushion, elastic module of pile, replacement ratio, distribution of soil layers, are analysised in details with numerical analysised methods. The influence on loading and settlement of those parameters is stated clearly, which offered referencing datum for optimization design.Finally, optimization model about CFG pile composite foundation is established which is subjected to the dual controls of bearing capacity and displacement employing optimization theories. Based on the theory of elastic-plastic mechanics, the correspondence equations of vertical deformation of pile is deduced with simplified condition, and a settlement formula taking account of the influence of pile length and replacement ratio is put forward. Moreover, the calculation formula and choosing method are deduced. With the help of mathematical software Matlab, an optimization design is carried out by solving the semi-infinitely constrained multivariable nonlinear function, and the results are compared with original design.