# Experimental Study on Pullout Behavior of Coir Geotextiles Based on Transparent Soil
## 1 Introduction  
Geosynthetic materials have been widely used in geotechnical engineering and other fields because of their low cost and good mechanical properties. Geosynthetic materials mainly rely on the interfacial friction between the reinforcement and the soil to play a role. Clarifying the interaction law between the reinforcement and the soil is crucial for clarifying the reinforcement mechanism. The pullout test is an important means to study the interfacial properties of the reinforcement and the soil. Many researchers have studied the soil-geosynthetic interaction using the pullout test. [PERSON] et al. [1] used Mixed Recycled Aggregate (MRA) and Polymer Strips (PS) as filler and found that the value of the apparent interfacial coefficient of friction was higher in dense conditions and decreased by 70-80% in loose conditions under a large pullout test. [PERSON] et al. [2] carried out pullout tests on geogrids reinforced with small metal plates, and the results showed that the pullout force increased significantly with the increase in the height of the small metal plates and the distance from the pullout load. [PERSON] and [PERSON] [3] carried out pullout tests with sandy soils and clays, respectively, and analyzed the interfacial parameters between the geogrids and the different fillers. [PERSON] et al. [4]observed the rotational movement of sand and gravel during the test and explored the effect of the geogrid on the pullout force through a large number of pullout tests. [PERSON] et al. (2020) conducted a pull test on soil reinforced with geogrids with different apertures, and the results showed that, compared with the geogrids with small apertures, the geogrids with large apertures had a better reinforcement ability. [PERSON] et al. (2020) added three different reinforcement materials, namely geogrids, geotechnical composite reinforcement materials, and geotextiles, to the granite residual soil, and the research results showed that the peak pullout force of the geogrids was the highest. [PERSON] et al. (2020) studied the influence of the angle of geotextile wrapping anchorage on the pullout force through the pullout test and found that, as the base angle decreased, the initial pullout force formed in the early and middle stages of pullout became larger, and as the top angle increased, the final pullout force, reached at the end of the pullout test, became larger. Some scholars have used transparent soil technology to carry out pullout tests and study the interface characteristics of reinforced soil in the geogrid (2020; 2020; 2020). However, all the above studies are aimed at generally common geosynthetics, which produce pollution during the production process and do not degrade easily inside the soil body. In this paper, several studies on soil reinforcement with different fiber geotextiles are listed, as shown in Table 1 (2019, 2019, 2019, 2019, 2019, 2020). As an environmentally friendly material, natural fiber fabrics need to be promoted and developed. The coir geotextile, as a representative natural fiber fabric, has excellent mechanical properties and durability. Methods to improve the durability of coir fibers and protect natural materials from biodegradation include the application of kerosene (2019), the application of cashew shell liquid oil (2019, 2020), lime treatment (2020), chemical reagent treatment (2020), and so on. Scholars have already used coir geotextiles as reinforcing materials in geotechnical engineering. [PERSON] et al. (2020) studied the influence of different forms of coir geotextiles on the load settlement characteristics of a sand bed on a square foundation, and the results showed that, for the same amount of material, the performance of the geocell-reinforced soil improved more than that of the flat form. [PERSON] et al. (2020) carried out monotonic loading tests of coir geotextiles reinforcing a very loose sand layer.