Concise semi-analytical solution for group piles impedance function and generalized group factor analysis considering SSI effect

It is foremost to investigate group piles dynamic response for large nuclear island structure considering high-precision soil structure interaction (SSI). However, the existing group piles effect obtained using static stiffness cannot reflect to the frequency dependence, and the spatial coupling characteristics of far-field artificial boundary limits the efficient and fine impedance function computation for large piles under complex foundation conditions. In present paper, a refined impedance function procedure for large-scale group piles is built on the scaled boundary finite element method (SBFEM). The far-field stiffness matrix is made to localize the spatial coupling using decoupling technique, a Runge-Kutta search strategy on frequency with zero-frequency starting is developed to obtain the complete stiffness matrix, and a generalized group factor calculation is proposed. The accuracy and effectiveness are proved with the cases of impedance function for small-scale group piles. At length, some fine large-scale nuclear island group piles model is investigated. All cases demonstrate that the pile impedance function, especially under the condition of layered ground, presents very obvious frequency correlations in the simulation of large-scale nuclear island group piles, which further confirms that the provided method has good engineering applicability.