Studies on the Soil Moisture Distribution in the Slope Banked by Decomposed Granite Soils and Characteristic of Mechanical Strength of Root Mat of the Torf Grass

Abstract

For the purpose of clarifying the mechanism of water movement in the decomposed granite soil (Masa) slope, change of soil moisture tension and groundwater level has been investigated by making use of the tensiometer and groundwater surveying pipe. The characteristics of mechanical strength of root mat of surface layer of the slope have been examined through the vane shear test and the direct shear test.
The conclusions obtained are summarized as follows:
1) The soil moisture tension and groundwater level change remarkably with time.
2) The soil moisture gathers and strages at the boundary layer between ground surface and banking layer as well as at the lower part the slope.
3) There are many cases of collapse in the boundary layer and the lower part of slope.
4) The strength constant of the root mat with many roots and stems is larger than that of the soil mat (ground surface).