|Budget Amount *help
¥1,700,000 (Direct Cost : ¥1,700,000)
Fiscal Year 1997 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1996 : ¥800,000 (Direct Cost : ¥800,000)
The negative porewater pressure (suction)exists in the natural slopes in fine day and contributes to the slope stability. In rainy days, the porewater pressure rises to the positive values and the stability of the slope may be lost. If the geo-textiles or the drainpipes with capillary membrane are embeded, negative porewater pressure may remain in the slope even on rainy days and stability of the slope can be kept. The geo-textile should have capillary tension more than 1m waterhead. According to the test results, there are no applicable materials directly. However, if a few geo-textiles are compressed together and a new geo-textile having high density is obtained, the problem will be solved. It is necessary to cover the slope surface by a sheet in order to keep the textile-end dry. When vacuum pressure applies to the backside of the sheet, slope surface is pressed by the atmospheric pressure and slope stability increase. Moreover, the soils of the slope may change to unsaturated condition.
According to the triaxial tests, the strength of the soils increases due to consolidation of vaccum pressure and due to occurrence of unsaturated condition. Strength increase ratio reaches to 10%. It is necessary to arrange the geotextiles in order to introduce vacuum pressure into the slope.