## 4 Conclusions  
Mercerization and bleaching treatments applied to nonwoven coir geotextiles altered their physical properties. Mercerization made the color of the nonwoven coir geotextile lighter and more vibrant while bleaching made the color much lighter. As seen in the SEM micrographs, both treatments reduced the thickness of the coir geotextiles, since the impurities and some biological components such as surface wax, lignin, and hemicellulose were removed. On the other hand, the removal of such components caused an increase in their tensile strength. Under the exposed conditions, mercerized coir geotextiles are better than bleached coir geotextiles because they are more resistant to the effects of degradation. Bleached coir geotextiles are better for unexposed conditions, but these conditions are unlikely to occur, as geotextiles are commonly placed in the field and can be exposed to numerous factors. The grab-breaking test revealed that the treatments effectively increased the tensile strength of the coir geotextiles. Results from the unexposed condition show that the bleaching treatment resulted in the greatest tensile strength, followed by mercerization, in comparison to the untreated samples. Exposure to field and groundwater conditions also increased the grab-breaking strength of nonwoven coir geotextiles. For all treatments, the exposed condition showed a higher value of grab-breaking strength than the unexposed condition. The CBR puncture test provided a different result from the grab-breaking test. For the unexposed, field condition, and groundwater exposure scenarios, the untreated specimens showed the most significant puncture resistance as compared to the treated samples. Removing surface impurities and biological components caused by the treatments led to a reduction in thickness, which decreased the puncture resistance of the nonwoven coir geotextiles. The nonwoven coir geotextiles were incorporated into a slope stability model using Rockscience Slide2 version 9.017 software and were shown to improve the stability of the slopes. The amount of spacing between the geotextiles is an essential factor when it comes to soil reinforcement. With the same spacing conditions as the synthetic geotextile, all of the coir geotextiles used for reinforcement have a safety factor slightly lower than that obtained for the synthetic geotextile but still show an improvement as compared to the unreinforced slope. Nonwoven coir geotextiles have a comparable strength with that of some synthetic \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatment-Exposure** & \
\begin{tabular}{c} **Allowable Tensile** \\ **Strength (KN/m)** \\ \end{tabular} & **Spacing (m)** &
\begin{tabular}{c} **Number of** \\ **Geotextiles** \\ \end{tabular} \\ \hline Untreated–Unexposed & 0.58 & 0.084 & 392 \\ \hline Mercerized–Unexposed & 0.64 & 0.095 & 347 \\ \hline Bleached–Unexposed & 0.83 & 0.120 & 275 \\ \hline Untreated–Field Condition & 0.85 & 0.124 & 266 \\ \hline Mercerized–Field Condition & 1.04 & 0.150 & 220 \\ \hline Bleached–Field Condition & 0.92 & 0.133 & 248 \\ \hline Untreated–Groundwater & 0.68 & 0.099 & 333 \\ \hline Mercerized–Groundwater & 1.34 & 0.198 & 166 \\ \hline Bleached–Groundwater & 0.95 & 0.140 & 235 \\ \hline Synthetic Geotextile & 1.98 & 0.300 & 110 \\ \hline No Reinforcement & — & — & — \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Summary of the requirements of coir geotextiles for slope reinforcement with a target factor of safety of 1.5.  
geotextiles such as nonwoven geotextiles. Under short-term loading conditions, it can be concluded that coir geotextiles can be effective as slope reinforcement. We recommend future studies of the real-life application of coir geotextiles as soil reinforcement for slopes to determine their onsite performance. Future studies can include the evaluation of the most well-suited construction methods when using coir geotextiles.