Soil mechanics for unsaturated soils is a newer technique. In Taiwan, this research is not many, but it’s importance is discovered. Therefore, in this research, test apparatuses of unsaturated soil are set up first, and research the procedures of soil-water characteristic test. Then, the soil-water characteristic curves of lateritic soil in Taiwan are found, and discuss the matric suction, high and low plastic, and void ratio of influences on soil-water characteristic curve. At last, numerical analysis uses PCSTABL5 program, and analyzes the heights and degrees of slope, and depths and degrees of groundwater of influence on stability of global slope. I hope that the result in this research can be applied design of engineering in lateritic soil terraces, and engineer can use to reference.
