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

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.