Long-term in situ scientific experiment: Demonstrating the slope protection effects of loess ecological materials

Ecological materials are increasingly being applied in the loess slope protection, and the time-dependency deterioration of materials is an important criterion in evaluating their protective effects. Taking polypropylene fiber and guar gum as examples, the protection tests of these two ecological materials were carried out for a typical bare cut-slope on the Loess Plateau in this study. We quantified the erosion deterioration based on the approach of LiDAR, and the deterioration processes of both the ecological materials were then comprehensively evaluated. Results showed that both the materials could generate good protective effects on the test slopes, and the guar gum mixed soil (GGS) was slightly better than polypropylene fiber reinforced soil (PFS) at initial time. However, the two materials deteriorated diversely with the increasing service time. The scouring erosion was mainly observed in PFS, which is different to the surface spalling observed in GGS, and the erosion mass presented different stepwise growth along the slope downward. In addition, the protective advantage of GGS was decreasing and even disappearing over time. Revealed by the dry-wet cycle tests, the rapid attenuation of disintegration resistance of PFS and shear strength parameters of GGS were the main reasons leading to the different deterioration of the two materials. For evaluating deterioration behavior of slope protection materials, the time-dependency deterioration model was furthermore established by combining the average intensity of effective rainfall as well as the disintegration rate and shear strength parameters of slope protection materials. Thus, the quantitative prediction on the deterioration process and the protective effect of slope protection materials were realized, with results indicating that the influences of disintegration rate, cohesion, and internal friction angel enhanced successively on the promotion of slope protection materials. This study is of great significance for revealing the deterioration mechanism and promoting continuous improvement of slope protection materials.