This research aims to examine the Soil-Water Characteristic Curve (SWCC) for residual soils formed from shale formation, and the relevance of the SWCC and the degree of weathering
are discussed. The FX model (Fredlund and Xing, 1994) is used to describe the Soil-Water Characteristic Curve of the residual soil, and the parameters ( a , m, n) in the FX model are back-calculated. A pressure plate apparatus is used to obtain the SWCC for the residual soils at various
depths. In addition, the soil particle distribution curve is drawn for the residual soil. The degree of weathering affects the SWCC of the residual soil. Water may dissipate more readily in the pore at low suctions for the soil with a higher percentage of coarse particles. a parameters, n parameters, and m parameters, used in the FX model, for the residual soil formed from shale are 7~9 kPa, 1~1.27, and
0.385~0.42, respectively. The relationship between the characteristics of the soil particle distribution curve and the physical properties and parameters ( a , m, n) of the FX model is established in this paper.The parameter “ a ” in the FX model decreases with increasing initial void ratio of the soil. Parameter m” increases with the effective size D10. Air-entry values decrease with the effective size D10. The parameter “n” in the FX model increases with the slope gradient at the middle portion of the soil particle distribution curve.
Key Words : Residual soils, soil-water characteristic curve, soil particle distribution curve, pressure plate test.