Differential settlements of piled raft foundation: numerical simulations, empirical equations and design charts

Abstract

Piled raft foundations are widely adopted for different kinds of infrastructure projects due to their high bearing capacity and deformation control efficiency. However, differential settlement which is critical to structural integrity remains inadequately addressed in existing design methods. This study employs three-dimensional finite element simulations to systematically analyze the influence of soil type, pile configuration, raft stiffness, and load distribution patterns on differential settlement. A novel parameter, the relative flexural ratio (defined as the angular distortion normalized by average settlement, θr/wave), is proposed to characterize the differential settlement behavior. Parametric studies reveal that the relative flexural ratio exhibits strong normalization with piled raft stiffness (Kr), with load distribution patterns being the dominant influencing factor. Empirical equations and design charts linking θr/wave to Kr are established for three typical load types (central, edge, and uniform). The reliability of the proposed design charts has been verified by three published case histories. Based on the design charts and the empirical equations provided in this paper, the distribution range of the maximum differential settlement of a piled raft foundation can be quickly obtained by calculating the average settlement of the piled raft foundation, offering a practical tool for preliminary differential settlement estimation in engineering design.