Three-dimensional soil–foundation–superstructure interaction analysis of nuclear building supported by combined piled–raft system.

Abstract

Recently, few nuclear facilities have been proposed on soil sites worldwide. Controlling the overall and differential settlement is a difficult task for a nuclear structure that rests on a soil site. Under these circumstances, a combined piled–raft foundation (CPRF) provides the required level of performance with a significant cost saving compared with a pile foundation. The combined system involves complexities in the interactions between the soil–pile–raft and superstructure system. The literature focuses on simulating the interactions between pile, soil, and raft. Until recently, the behavior of a CPRF that supported a heavy and massive structure had not been well studied and understood. A combined three-dimensional (3D) model of soil–pile–raft–superstructure systems will be developed in this study that considers the soil and interface nonlinearity along with the complex superstructure geometry. The modeling approach for the piled raft system will be validated using the standard benchmark problem and field case histories. Various aspects of a CPRF for a typical nuclear building (NB) will be investigated, such as the effect of the depth of soil medium, comparison of the behavior of the raft foundation, pile foundation, and CPRF, contact pressure distribution, pile behavior, soil behavior; and various performance indicators. The presented systematic procedure to configure the CPRF system could be useful in similar practical applications. This study indicated that the stiffening of the superstructure and sequential construction has a beneficial effect on the combined system. The findings of this study could be useful to frame the general guidelines for the economical design of CPRF systems.