The use of recycled polyester (rPET) in construction materials offers significant benefits, including energy conservation, cost reduction, and decreased solid waste. This study compares the performance of rPET with that of virgin polyester (vPET) products. Therefore, two main testing programs including pull-out tests and creep performance tests were carried out in order to determine the interfacial properties of the geogrid-reinforced soil and time-dependent manner of the geogrids, respectively. Broadly speaking, this study showed that the performance of rPET geogrid is comparable with vPET geogrids. Pull-out tests revealed that pull-out resistance of both vPET and rPET geogrids were roughly the same and the vPET geogrid mostly had lower dilation angles in comparison with rPET. Moreover, based on the performance creep tests, it was understood that the long-term mechanical behaviour of rPET does not differ from the long-term behaviour of vPET products.

Coal-bearing soil slopes are associated with a high risk of landslides when subjected to high soil water content. Steel bars have been used as soil nailing for slope stabilization; however, corrosion may occur in an aggressive environment. Glass fiber reinforced polymer (GFRP) and basalt fiber reinforced polymer (BFRP) bars have higher resistance to corrosion and could be alternatives to steel bars, but their elastic modulus and bonding strength with cement concrete are inferior to steel bars, which may result in lower reinforcement effects against landslides and hence require further investigation. In this study, the mechanical properties of different types of bars were investigated using tensile tests. The mineral composition of the soil samples was analyzed. Subsequently, pull-out tests were conducted on three types of bars (steel, GFRP, and BFRP) embedded in grouts in the soil. Up to 38 test scenarios were investigated, and the results were statistically analyzed using an analysis of variance test. The effects of several factors were studied, including the bar type, water content, soil compaction degree, and soil surcharge. The results showed that the bar type had an insignificant effect on the maximum pull-out loads, indicating the feasibility of using GFRP and BFRP bars as alternatives to steel bars for soil nailing in coal-bearing soil slopes. The reinforcement effect can be weakened by rainfall or drought events and enhanced by higher compaction energy and surcharge loads.