被膜シートを敷設した斜面における降雨中の水分変化に関する実験的研究

Experimental Study on the Change of Soil Moisture under the Protective Sheets Designed to Prevent Soil Erosin Caused by Rainfall

Creators Kusaka Tatsuro

Creators Fukuda Mitsuo

Creators Terashima Haruo

Creators Roy Kingshuk

To investigate the effectiveness of protective sheets designed to prevent soil erosion caused by rainfall,two experiments were conducted. Rainfall was artificially generated by a rainfall simulator in order to observe the variations of tension of soil moisture beneath the protective sheets for a given period of rainfall. The another experiment was designed to pbserve the traced out flow patterns through the soil and the protective sheets using colored injected materials and a transparent water channel apparatus. Three types of protective sheets were spread out on three adjacent plots composed of MASA soil with equal dimensions of 18^。 Slope, 10 m length, 1 m width and 50 cm depth. The intensity of the rainfall varied within the limit of 25 mm for 4 hours to 200 mm for 1 hour. The tension of soil moisture at the points of 1m, 5m, 9m from the downward ending of each plot and 10cm, 25cm, 40cm beneath the sheet of each points were recorded automatically by the tensiometers. Simultaneously, the volume of runoff, seepage and the mass of sediment from these plots were also measured. From the results of the first experiment, it was found that, in the cases of rainfall-intensity 50 mm and 100 mm, the tension of soil moisture at the point of 10 cm depth, started to decrease first and followed at the points of 25cm, and 40cm respectively. As a result, the water-table began to rise. Finally, when the water table reached the soil surface, the volume of runoff and soil loss reached at their maximum values. In the cases of 150 mm and 200 mm, runoff and soil loss started to occur about the same time the rainfall was applied. The results obtained from the second experiment showed that the fibrous sheets prevented rill-formation by absorbing water and dispersing the flow due to their high permeable characteristics.

[ISSN]0513-1715

[NCID]AN00244250