Effects and mechanisms of erosion control techniques on stairstep cut-slopes

Many erosion control techniques, such as stone pitching, concrete revetment, and geotextile covering, have been effective at protecting cut slopes along roads or railways. However, these methods are expensive and hard to operate for high stairstep cut-slopes. To investigate the efficiency of several easily implemented and low-cost techniques, five plots with different treatments were built on stairstep cut-slopes. The five treatments consisted of vegetation coverage on platforms, counter-slope on platforms, upslope drainage, a control check (CK), and a comprehensive treatment of the first three techniques. During nineteen recorded rainfall events from June 2015 to August 2016, the runoff and sediment amount of each plot was measured. Soil water content and shear strength of the 2-m depth profile at each plot after the occurrence of rainfall and evapotranspiration were also investigated. The results indicated that runoff and the sediment amount from the five plots increased with an increase in rainfall amount with a threshold of 5 mm rainfall to produce sediment loss. Compared with the CK, the comprehensive and upslope drainage treatments had a larger reduction in runoff and sediment amount than those of the vegetation and counter-slope treatments. After either rainfall or evapotranspiration, the vegetation and comprehensive treatments had the highest soil water content, and the upslope drainage treatment had the lowest soil water content. The infiltration capacity followed the order of upslope drainage < CK < counter-slope < vegetation < comprehensive treatment. The shear strength of soil logarithmically decreased with soil water content in the five plots, and a critical water content of 12% determined the rate of change for shear strength. Finally, the upslope drainage technique was determined as the preferred recommendation to protect high stairstep cut-slopes.