Influence of hydraulic properties to residual soil

Tropical country such as Malaysia experienced high intensity and long period of rainfall, which is the main factor of slope failure. The increasing of seepage subjected by rainfall not only distress suction distribution, but also affects hydraulic properties of soil lead to the decreasing of soil strength. This also leads to soil slope failure. The main hydraulic properties for soils are Soil-water characteristic curve (SWCC) and hydraulic conductivity, k. The relationship of these parameters is highly influenced by tropical soil, thus contributes to soil instability phenomenon. The main objective of this paper is to study the relationship between soils' hydraulic properties and particle size distribution (PSD). Four types of soils investigated in this research include one sample taken from Universiti Kebangsaan Malaysia (UKM)'s reserved forest, and three samples were commercially obtained. Other than soil basic properties, pressure plate extractor and permeability tests were conducted for SWCC and permeability, respectively. Tests show that different types of soils demonstrate different characteristic of SWCC and hydraulic conductivity. Result also shows that PSD has the influence and affect the result of hydraulic properties of soils. This study is expected to enhance the understanding of complex phenomenon of residual soil instability.