Rainfall Infiltration and Runoff Characteristics of an Unsaturated Volcanic Soil under Grass Cover

Vegetation is increasingly used in geotechnical practice in order to reduce the amount of infiltration on the soil. However, elaborate studies and numerical methods considering the influence of vegetation on rainfall infiltration and soil slope stability have been very limited. In order to understand the mechanism of seepage behaviour and investigate differences in the amount of infiltration and runoff water between bare soil and grassed soil, a series of column tests and numerical analyses were performed. Experimental test results reveal that the grass cover plays an important role in minimizing the infiltration. Furthermore, soil-water retention and seepage behavior under unsaturated condition of grassed soil differ from those of bare soil. In this study, a numerical simulation approach was proposed and it was found to be useful by reproducing the experimental test results with good agreement.