Parametric Study of Piled Raft Foundations: Performance in Layered Soil Subjected to Uniform Vertical Loading

Abstract

Rapid urbanization has necessitated the construction of large civil structures, often on soft soil sites, that can cause settling, especially in urban areas with limited rock sites. Strict safety regulations require minimal differential settlement in high-rise buildings, despite their considerable weight. For the past four to five decades, piled raft foundations have been successfully used throughout the world to maximize civil engineering structure foundations by creating a composite foundation in which the piles are used as settlement reducers and share the load from the superstructure with the raft. In these foundations, piles act as settlement reducers and share the superstructure's load with the raft. Due to the complex soil-structure interaction in pile raft foundations and the absence of field data, numerical approaches are frequently needed. In this study, the load-settlement behavior of piled raft from previous numerical works was analytically simulated to validate the 3D finite element model. The performance of a rectangular combination piled raft system is evaluated in layered soil subjected to uniform vertical loading. The analysis is conducted using the powerful finite element-based program Plaxis 3D to examine the effects of various parameters. A parametric study is also carried out to investigate the response of piled-raft foundations, including the influence of raft thickness, number of piles, pile length, spacing of piles, and pile diameter. It was observed that by increasing raft thickness from 0.7 to 1.7m, the differential settlement was reduced by 78.21% for the case of the 16-pile number. However, the maximum settlement increased by 2.81%. By increasing the number of piles from 4 to 16, the maximum settlement amount was reduced by 22.09% for 4D pile spacing. Additionally, from the total settlement reduction obtained by increasing pile length, a 19.49% reduction was achieved by increasing the pile length from 9m to 15m in the case of 5D pile spacing. Hence, the findings from the current research can serve as a framework for examining and developing large piled-raft foundations.