The Variation of Pore-water Pressure in the Sidewall of the Gully developed on Mountainous Slope in a Temperate Climate, South Korea: Preliminary Study

It is critical to monitor slope hydrology in order to apply to evaluate the matters of soil loss and slope stability. Matric suction in an unsaturated soil, specially, influences the shear strength of the material. Thus, we have firstly monitored to know the variation of the matric suction on the sidewall of the gully, however the objective to this study is ultimately to relveal the effect of pore water pressure on the process of the sidewall failure. For most of the monitoring period, unsaturated hydraulic gradients are downward. The temporal variation in pore-water pressures increase with increasing soil depth, but the response on the matric suction to rainfall occures mainly the soil at the shallower depth. Moreover, the variation of pore-water pressures along the soil depth is related with the rainfall intensity, and the latent period of martic suction as rainfall increase with soil depth. Consequently, compressed air, formed by downward water movement, at lower part of soil influenced the reduction of reaction velocity along the soil depth. Keywords: pore-water pressure; vertical and temporal variability; vertical unsaturated flow; slope hydrology.