Elastic–Plastic Constitutive Relationship of Polymer Fiber–Reinforced Clay Considering the Effect of Anisotropic Distribution

Abstract

Due to their advantages of high rupture strength and long service life, polymer fibers are often used for soil improvement. However, there is no consensus on how the mixing of discrete polymer fibers affects the stress–strain relationship of clays. In this study, a constitutive relationship of polymer fiber‒reinforced clay was established on the basis of the stress–strain relationship between clay and polymer fibers. The elastic–plastic unified hardening (UH) model was employed, and the fiber contribution was introduced based on the UH model. The constitutive relationship of polymer fiber‒reinforced clay considers the anisotropic distribution of the discrete fiber orientation and the relative sliding between the fibers and clay matrix. The model was verified by referring to the results of consolidated undrained (CU) and consolidated drained tests of typical polymer fiber‒reinforced clays in previous studies. A series of CU tests on rubber fiber‒reinforced clay were conducted to validate the model further. The ratio of the simulated results to the experimental results gradually approached 1 with increasing axial strain. The constitutive relationship of polymer fiber‒reinforced clay could provide satisfactory results. Polymer fiber mixing increases soil strength and enhances the properties of problematic soils, which makes the problematic soils more valuable for engineering applications. Studies have shown that the fibers in the soil tend to be distributed horizontally after the compaction process. With the anisotropic distribution of fiber orientation considered, the authors established a numerical calculation method for the stress–strain relationship of polymer fiber‒reinforced clay. A major objective of this work was to allow the use of computerized numerical analysis methods when performing mechanical analyses of polymer fiber‒reinforced clay, which avoids the need to conduct a large number of shear tests. In this study, a series of consolidated undrained tests of rubber fiber‒reinforced expansive clay were conducted. With the data collected, the numerical calculation method for the stress–strain relationship of polymer fiber‒reinforced clay was verified, and the numerical results agreed with the test results better.