The Strength Law of Coconut Shell Fiber–Reinforced Soils Based on the Hardin–Drnevich Model

A large diameter triaxial specimen of 61.9 mm was made by mixing coconut shell fibers with red clay soil. The shear strength of coconut shell fiber–reinforced soil was investigated using a dynamic triaxial shear test with confining pressure in a range of 50–250 kPa, a fiber content of 0.1%–0.5%, and a loading frequency of 0.5–2.5 Hz. The Hardin–Drnevich model based on the coconut shell fiber–reinforced soil was developed by analyzing and processing the experimental data using a linear fitting method, determining the model parameters a and b, and combining the influencing factors of the coconut shell fiber–reinforced soil to improve the Hardin–Drnevich model. The results show a clear distinction between the effects of loading frequency and fiber content on the strength of the specimens, which are around 1 Hz and 0.3%, respectively. Hardin–Drnevich model based on coconut shell fiber–reinforced soil can better predict the dynamic stress-strain relationship of coconut shell fiber-reinforced soil and reflect the dynamic stress-strain curve characteristics of the dynamic stress-strain curve coconut shell fiber-reinforced soil.