Constitutive modeling and testing of interface between backfill soil and fiber-reinforced polymer

Geomaterials behave differently under different types of loadings, such as compression, shear, or tension; they exhibit weaker response in tension. To increase the tensile and shear strengths of the soil, different methods of reinforcement, such as geosynthetics, have been used in earth structures such as retaining walls, earth dams, and slopes. The use of geosynthetics has attracted the attention of engineers and researchers in recent years. However, there are some significant problems associated with geosynthetics, such as low tensile strength, creep, and for some applications, a low stiffness modulus. In this research, a geocomposite (GC), made of carbon fiber-reinforced polymer (CFRP), is proposed and studied. The interface properties of the CFRP and backfill soil are investigated experimentally using a cyclic multidegree-of-freedom (CYMDOF) device. Then an elastic-plastic constitutive model, the hierarchical single surface (HISS), is used to characterize the behavior of the interface between the CFRP and backfill soil. The constitutive model is verified by predicting the laboratory behavior of interface for tests used to find parameters and comparing that to independent tests. Based on the investigation, CFRP can be considered to be appropriate and beneficial as reinforcement in earth structures, because it has relatively high friction angle, high tensile strength, high Young's modulus, and high resistance to aggressive environment.