Controlling Consolidation Settlement in Soil Using Foamed Material

Abstract

Polyurethane (PU) foam is an alternative controlling consolidation method to resolve the problem of consolidation. In this study, a consolidation laboratory test was executed to determine the consolidation in soil improved with PU foam. This research aims to assess the effectiveness of PU foam in mitigating consolidation settlement. By conducting comprehensive laboratory testing and analysis, this study seeks to provide valuable insights into the practical applications and potential advantages of polyurethane spray in soil stabilization, with the ultimate goal of contributing to advancements in civil engineering and construction projects. The consolidation reduction is carried out by excavating the soil at a shallow depth and mix with PU foam. The performance of different percentages of PU foam as a consolidation controller is evaluated. The comparison is made by mixing PU foam with saturated clay and water to determine the reduction in consolidation by evaluating different parameters of soil like final deformation compression index etc. The percentage of mixing PU foam to soil varies from 3% to 5%. The different parameters like compressibility index, coefficient of volume compressibility, void ratio, and final deformation values for PU mixed with saturated soil are adopted in this study with the respective equations. The settlement reduces significantly up to a certain limit of PU foam and again increases beyond that limit of PU foam for the saturated soil.

Introduction

The text focuses on the problem of soil settlement in cohesive soils (especially clay), which can cause structural failures in buildings, dams, and embankments due to slow and uneven consolidation. Since clay has low permeability, settlement occurs over a long period, making it critical to improve soil properties using stabilization techniques.

Traditional soil improvement methods include the use of additives such as lime, cement, fly ash, bitumen, silica fume, and biopolymers. Previous studies show that these materials can reduce compressibility, improve strength, and enhance consolidation behavior. Other approaches like construction waste, waste tires, grouting, and chemical stabilization have also been explored. However, each method has limitations related to cost, effectiveness, and long-term performance.

A key research gap identified is the limited understanding of foamed materials (e.g., polyurethane foam) in soil stabilization, particularly:

• Interaction between foam and soil particles,

• Long-term degradation and stability,

• Scalability for practical applications,

• Lack of standardized testing methods.

The study aims to evaluate the effectiveness of foamed materials in reducing soil consolidation and settlement, while also considering cost implications.

The study area is Bannu, Pakistan, where soil samples were collected from multiple locations. Samples were divided into untreated and foam-treated groups for comparison.

The methodology involves laboratory experiments using oedometer (consolidation) tests to analyze soil behavior under load. Key steps include:

• Preparing soil samples,

• Applying incremental loads,

• Allowing drainage and measuring settlement,

• Recording deformation over time.

Important parameters analyzed include:

• Compression Index (Cc): Indicates soil compressibility,

• Coefficient of Volume Compressibility (mv): Measures volume change under pressure.

Results indicate that the addition of polyurethane (PU) foam reduces compressibility and settlement, as seen by decreased values of Cc and mv.

Conclusion

This research study employed an experimental methodology, utilizing a laboratory-based investigation to examine the effectiveness of foamed materials in controlling consolidation settlement in soil. Soil samples of varying types were collected and prepared according to standards, then mixed with selected foamed materials and compacted it. Consolidation tests were performed on treated and untreated soil samples using a consolidometer, and the resulting data were analyzed statistically to compare the consolidation settlement of soil with and without foamed materials. From the research carried out to check the effect of PU foam on the consolidation behavior of saturated clay after complete testing and analysis of results certain conclusions may be drawn. These concluding remarks are stated below. 1) After making the comparative analysis by adding PU foam the consolidation settlement was found to reduce significantly which is an encouraging sign as far as the stability of the foundation is concerned. 2) As it is clear from the previous studies PU can be successfully used for enhancing other properties of soil. Therefore, it is highly recommended for soil stabilization 3) The percentage of PU foam may not be increased beyond 3 % as it reverses the magnitude of deformation.

References

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Copyright

Copyright © 2026 Mansoor Shah, Amir Ullah , Basir Ullah, Mohsin Khan, Shafi Ur Rehman, Ali Akbar, Zia Ur Rahman. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.