Effects of polyurethane foam on the behaviour of collapsible soils

Ahmed S Abdulrasool,Saad F A Al-Wakel

doi:10.1680/jgere.21.00005a

Abstract

Collapsible soils such as gypseous soil are problematic in geotechnical engineering because their volume changes significantly upon saturation. Foundations constructed on gypseous soil undergo sudden and large settlement if the underlying soil experiences unanticipated moisture. The present study aims to improve the gypseous soil behaviour so that it can be used to support shallow foundations. To understand the mechanisms of stabilisation better, a laboratory study is performed to evaluate how polyurethane foam in different amounts influences the volumetric strain, collapse potential and mechanical behaviour of gypseous soil. Physical models of a footing on treated gypseous soil with polyurethane foam are examined to determine the effective treatment zone. Based on the obtained results, 3% polyurethane foam can be recommended to improve the gypseous soil behaviour; the particular reason is its effectiveness in decreasing the change in volumetric strain and collapse potential. The present study develops a theoretical approach that depends on a non-dimensional parameter to predict the ultimate bearing capacity for a footing on the surface of treated gypseous soil using the existing conventional theories.

Highlights

Soils can be problematic in geotechnical applications because they collapse, undergo excessive settlement and have a distinct loss of strength or solubility (Bell and Culshaw, 2001); one of these soils is the collapsible soil. Clemence and Finbar (1981) defined the collapsible soil as any unsaturated soil that goes through a radical rearrangement of particles and great loss of volume upon wetting with or without additional loading.In general, sudden changes in volume develop in collapsible soils, which leads to collapse due to the increase in their moisture contents with or without loading; this occurs when the degree of saturation reaches above 50% (Abbeche et al, 2010)
Compressibility and collapsibility behaviour The results of the simple oedometer test on the samples of untreated gypseous soil shown in Figure 3 and gypseous soil treated with polyurethane foam (PF) (Figures 4–7) are presented in the form of e plotted against log s 0, where e and s 0 are the void ratio and effective stress, respectively
Effect of polyurethane foam The results obtained in this study indicate that treating gypseous soil with PF minimises the volumetric strain change compared with pure gypseous soil

Summary

Introduction

Soils can be problematic in geotechnical applications because they collapse, undergo excessive settlement and have a distinct loss of strength or solubility (Bell and Culshaw, 2001); one of these soils is the collapsible soil. Clemence and Finbar (1981) defined the collapsible soil as any unsaturated soil that goes through a radical rearrangement of particles and great loss of volume upon wetting with or without additional loading. The present study involves a detailed investigation of the behaviour of gypseous soil treated for the first time with polyurethane foam (PF), which can be used in a liquid state. Experimental tests are performed to study how PF affects the volumetric strain, collapse potential and strength of gypseous soil. A more comprehensive range of PF content (0, 0.75, 1, 3 and 5%) was used in performing oedometer tests to investigate how PF treatment affected the soil volumetric strain and collapse potential, which were considered an important aspect in this study. The same range of PF content was used to perform California bearing ratio (CBR) tests to investigate how the PF treatment affected the strength of the gypseous soil.

Part A Part B Part A Part B — Values

Limitations

Results and discussion

Conclusions