Numerical Study of Underpinning by Piles for Settlement Control of Strip Foundations

by M. Makarchian, Univ of Sydney, Sydney, Australia,
H.G. Poulos, (F.ASCE), Univ of Sydney, Sydney, Australia,

Document Type: Proceeding Paper

Part of: Vertical and Horizontal Deformations of Foundations and Embankments


A numerical study has been carried out of a simple idealized problem of a shallow strip foundation (both flexible and rigid) on clay underpinned by rows of piles. The work is directed towards the development of a more reliable, but practically useable, approach for the design of piles for underpinning work. The finite element method has been used for this analysis, with the soil treated as a two-phase elasto-plastic soil, so that soil failure and consolidation can be considered. Solutions have been obtained for the time-settlement behavior of the foundation after installation of the pile, and the influence on this behavior of pile length, time of installation, and applied load level are examined. It is found that the rigidity of the foundation has a significant effect on load transfer from the existing foundation to the newly installed piles. The results shows that piles installed within a rigid strip foundation are more effective than for a flexible foundation. Also, the earlier piles are installed, the less the final settlement, with more load being transferred to the piles.

Subject Headings: Numerical analysis | Pile settlement | Foundation settlement | Soil analysis | Soil treatment | Load transfer | Numerical methods | Underpinning

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