# Experimental Study on Pullout Behavior of Coir Geotextiles Based on Transparent Soil
## 2 Materials and Methods  
### Test Materials  
Transparent soil is a kind of artificial soil which is composed of solid particles and liquid with the same refractive index. In the present study, the solid particle material was fused quartz sand and the pore liquid was No. 15 and No. 3 industrial white oil mixed at a volume ratio of 1.5:1. Figure 1 shows the soil particle grading curves of transparent soil and natural sandy soil, and the particle grading curves of both were consistent. The shear strength characteristics of the transparent soil and the natural sandy soil were measured by a fast shear test. Figure 2 shows the shear-stress-shear-displacement relationship in the transparent soil and the natural sandy soil. It can be seen from Figure 2 that the characteristics of the transparent soil and the natural sandy soil were similar, and the shear strength increased with the increase in normal stress. Figure 3 shows the relationship between shear strength and normal stress in the transparent soil and natural sandy soil. As it can be seen from Figure 3, the internal friction angle of the natural sandy soil was  
\begin{table}
\begin{tabular}{c c c} \hline
**Types of Fiber Geotextiles** & **Impact on Strengthened Soil** & **Ref.** \\ \hline PP (artificial fiber) & Soil erosion control & [11] \\ \hline PE (artificial fiber) & Soil reinforcement & [12] \\ \hline PET (artificial fiber) & Soil reinforcement & [13] \\ \hline Jute (natural fiber) & Soil erosion control, drainage, filtration & [14] \\ \hline Water hyacinth (natural fiber) & Soil erosion control & [15] \\ \hline Cotton (natural fiber) & Soil erosion control & [16] \\ \hline Kenaf (natural fiber) & Soil reinforcement & [17] \\ \hline \end{tabular}
\end{table}
Table 1: Different fiber geotextiles.  
The coir geotextile was woven from the coconut shell fiber produced by the fruit of tall coconut trees. Figure 4 shows the physical picture of the coir geotextile, which had a grid-like structure similar to geogrids. Table 2 shows the basic physical characteristics of the coir geotextile, in which the linear density was mainly used to represent the thickness of the transverse and longitudinal ribs of the coir geotextile, while the gram weight was the mass of the coir geotextile per unit area. According to the research of [PERSON] [29], when the width of the fabric was 3/4 of the width of the pullout test box, the friction effect on the side wall of the pullout test box could be minimized. Therefore, the width of the coir geotextile in this article was set to 300 mm. The reservation distance between the coir geotextile and the transparent glass side panels on both sides of the pullout test box was 50 mm. The lubrication of the mixed oil and the small friction coefficient of the left- and right-side walls can further reduce the impact of the boundary effect. Figure 5 shows the tensile test curve of the coir geotextile. The ultimate tensile strength of the coir geotextile was 8.25 kN/m and the peak strain was 23.31%. When the coir geotextile was subjected to a 5% strain, the tensile strength was 0.75 kN/m and the corresponding stiffness was 15 kN/m. When a 10% strain occurred on the coir geotextile, the tensile strength was 2.63 kN/m and the corresponding stiffness was 26.3 kN/m.