Deep Soil Mixing Columns as Settlement-Reducing Elements in Sandy Soils: A Numerical Study
Publication: International Journal of Geomechanics
Volume 23, Issue 4
Abstract
The philosophy of designing piles as settlement-reducing elements causes the number of piles required beneath a wide foundation to be significantly reduced compared with conventional design methods. In this study, the behavior of deep soil mixing (DSM) columns used as settlement-reducing elements under the foundation of circular liquid reservoir tanks with large diameters (more than 50 m) in sandy soils of the Persian Gulf coast under axial loading has been investigated using a parametric-based finite element method (FEM) analysis in a Midas GTS NX environment. The parametric study includes 1 case with no improvement and 48 cases of improved soil with various configurations. The loading conditions are similar to those of a standard liquid tank with a large diameter. Variables such as area improvement ratios, DSM column floating ratios, and cushion layer thickness have been investigated. It has been found that increasing the thickness of the cushion layer, the floating ratio, and the area improvement ratio each contributes a certain amount to the overall reduction of the total and differential settlement values. However, under certain conditions, some factors, such as the area improvement ratio, have been found to have a reduced improvement effect. These factors, and their influence on the whole system, have been thoroughly investigated numerically in the parametric study, and in the two validation cases, the results of the FEM analysis have been compared with measured data from the field and small-scale tests. The results of gathered data from field tests and parametric studies have also been compared with empirical formulas provided by other researchers.
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Acknowledgments
The authors would like to acknowledge the collective funding of Fasa University and Iran University of Science and Technology for this project.
Notation
The following symbols are used in this paper:
- aS
- area replacement ratio of the column to soil;
- Df
- foundation’s diameter;
- EC
- elastic modulus of the column;
- ES
- elastic modulus of the soil;
- HC
- height of the cushion layer;
- HU
- height of the unimproved layer;
- IR
- area improvement ratio;
- LP
- length of the pile;
- n
- stress concentration ratio;
- S
- settlement of the natural ground;
- Scenter
- settlement of the foundation’s center;
- Smin ring
- minimum settlement of the foundation’s ring;
- S′
- settlement of DSM-improved ground; and
- δ
- normalized differential settlement.
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Published In
International Journal of Geomechanics
Volume 23 • Issue 4 • April 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: May 5, 2022
Accepted: Sep 9, 2022
Published online: Jan 24, 2023
Published in print: Apr 1, 2023
Discussion open until: Jun 24, 2023
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