# Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests
## 3 Results and Discussion
### Secant Modulus  
The secant modulus is defined as the ratio of the deviatoric stress to the corresponding axial strain at a particular point on the stress-strain curve. Based on this definition, the secant moduli of untreated soil, fiber-reinforced soil, lime-stabilized soil, and fiber-reinforced soil stabilized with lime were calculated at four small strain levels. The variations in these moduli with strain level are shown in Figure 4. In this figure, the characteristics of the variations vary from case to case. For fiber-reinforced soil and fiber-reinforced soil stabilized with 2% lime, the secant moduli increase with increasing strain level. For fiber-reinforced soil stabilized with 6% lime, an increase in strain level leads to a reduction in the secant moduli. However, no consistent trend is observed for either lime-stabilized soil or fiber-reinforced soil stabilized with 4% lime. The varied characteristics of the variations in these moduli can hardly be explained using the experimental evidence collected in this study, showing the need to conduct more relevant laboratory work.  
The secant moduli at a 1.2% axial strain level for untreated soil, fiber-reinforced soil, lime-stabilized soil, and fiber-reinforced soil stabilized with lime are shown in parallel in Figure 5, where the percentages represent the rates of increase in the secant moduli compared to that of untreated soil. Note that each of the percentages presented below the bars was calculated by adding  
Figure 3: Shear strength parameters for soil samples with additives of different contents: (**a**) cohesion and (**b**) angle of internal friction.  
the rate of increase in the secant modulus produced by fiber reinforcement to that produced by lime stabilization. From this figure, it is indicated that lime stabilization can increase the secant modulus of Hefei clayey soil at a 1.2% axial strain level. The increase in the secant modulus reaches a maximum of 249.2% at 4% lime content. On the other hand, the secant modulus is reduced by fiber reinforcement. The reduction in the secant modulus increases with increasing fiber content. At 0.6% fiber content, the reduction reaches 31.3%.  
Figure 4: Secant moduli at four strain levels tested at \(\sigma_{3}\) = 200 kPa: (**a**) samples reinforced with fibers or stabilized with lime and (**b**) fiber-reinforced samples stabilized with lime.  
Figure 5: Secant moduli at a 1.2% strain level tested at \(\sigma_{3}\) = 200 kPa: (**a**) 2% lime content, (**b**) 4% lime content, and (**c**) 6% lime content. The percentages represent the rates of increase in the secant moduli compared to the untreated one.  
Despite the fact that fiber reinforcement reduces the soil's secant modulus, a combination of fiber reinforcement and lime stabilization greatly increases the secant modulus. This increase in the secant modulus decreases with increasing fiber content when the lime content is kept constant. Meanwhile, keeping a constant fiber content, the increase in the secant modulus due to a combination of fiber reinforcement and lime stabilization reaches its maximum at a lime content of 4%. Besides this, the increase in the secant modulus due to a combination of fiber reinforcement and lime stabilization is greater than the summation of the respective increases in the secant modulus produced by fiber reinforcement and lime stabilization for all of the considered cases except for 0.2% fiber-reinforced soil stabilized with 2% lime. Therefore, the coupling effect of fiber reinforcement and lime stabilization on the secant modulus of the soil at a 1.2% strain level is that the presence of fibers improves the ability of lime to increase the soil's secant modulus.