This paper presents a comprehensive investigation into the behavior of combined pile–raft foundations (CPRF), utilizing a novel and efficient numerical model that integrates well-established geotechnical theories. A detailed parametric study was conducted, through which an expression for the settlement interplay coefficient is developed, clarifying the relationship between settlement and pile load ratios. This study also explores the impact of different pile–raft connection types (hinged and fixed), providing insights into their structural implications. In addition, a new parameter is proposed for accounting the relative cost between pile and raft installation, which integrates economic considerations into CPRF design by linking settlement behavior to material costs. The results offer a more refined design framework for designing efficient CPRF foundations, balancing technical performance and economic feasibility.
Brown et al. (2026) studied this question.