Study of Piled Raft Behaviour in Four Distinct Clay Types-PPT Presentation

PPT Presentation

Pdf Summary

This study examines the short- and long-term behaviour of piled raft foundations (PRFs) in four clays: Boston Blue Clay, London Clay, Shanghai Clay, and San Francisco Bay Mud. It considers 20 small- to medium-sized PRF configurations and overconsolidation ratios (OCRs) from 1 to 5. The analyses use three-dimensional finite-element modelling in ABAQUS, with Modified Cam Clay soil behaviour and coupled consolidation; the model was validated against centrifuge-test results.<br /><br />The study evaluates settlement over time, degree of consolidation, and maximum and differential settlements. PRF settlement develops in three stages: immediate settlement, followed by consolidation settlement that first follows a power-law relationship with time and later a logarithmic trend. Immediate settlement can be substantial relative to consolidation settlement, particularly in overconsolidated clay, and its magnitude is consistent regardless of how quickly the external load is applied.<br /><br />The degree of consolidation is largely independent of PRF geometry. OCR affects consolidation behaviour during the early stages, but has only a marginal influence once consolidation exceeds about 55%.<br /><br />Across the configurations studied, maximum settlement is approximately 24% greater than average settlement, while differential settlement is about 6% of the average. These estimates apply to PRFs of sizes similar to those analysed.

Keywords

piled raft foundations

settlement behaviour

consolidation

overconsolidation ratio

clay soils

finite element modelling

ABAQUS

Modified Cam Clay

differential settlement

centrifuge test validation