Stability of artificial soil aggregates for cut slope restoration: A case study from the subalpine zone of southwest China

The stability of soil aggregates is regarded as the key factor for soil erosion resistance on cut slopes of engineering works in serious debris flow disaster areas. Information on the stability of soil aggregates and related physicochemical properties on cut slopes is helpful to maintain the soil quality and slope stability. Therefore, in order to evaluate the stability of artificial soil aggregates for cut slope restoration, soil samples from three positions of a cut slope restored with artificial soil (upper slope, URS; middle slope, MRS; lower slope, LRS) and a nearby natural slope (NS) were analyzed. The results showed that the stability of soil aggregates (MWD, mean weight diameter; GMD, geometric mean diameter) of artificial soil on the cut slope (URS, MRS, LRS) was significantly lower than that of NS based upon fast wetting (FW) test and wet sieving. The values of MWD and GMD for slow wetting (SW) and mechanical breakdown (WS) tests in the four slopes had no significant difference. Among the three positions of cut slope, URS had the highest MWD and GMD, whereas MRS had the lowest corresponding value. Furthermore, >2 mm soil aggregates accounted for a major percentage of the total weight determined in all the tests for each slope. MWD for fast wetting increased with the increase in content of soil organic matter (SOM). Slaking was the main disruptive force leading to the breakdown of artificial soil aggregates, and FW was the best method to measure the stability of soil aggregates in these conditions. These results demonstrate that the SOM and the stability of soil aggregates on cut slope should be given more attention while conducting engineering works in serious debris flow disaster areas.