Effect of Slope Terrain on Distribution of Matric Suction in Unsaturated Slopes Subjected to Rainfall: Fid-Bau Portal

Effect of Slope Terrain on Distribution of Matric Suction in Unsaturated Slopes Subjected to Rainfall

Fan, Ch. / Hsiao, Ch.

This paper presents a field experimental study on the influence of slope terrain on the distribution of matric suction of the soil in unsaturated slopes subjected to rainfall. Instrumentation and testing programs were carried out in a slope with different terrains, i.e. planar slopes, gullied slopes, and ridge-like slopes. The matric suctions of the soil at a depth greater than 1.2m were measured using jet-filled tensiometers, and those less than 0.9m were measured using the filter paper method. The matric suctions of the soil along the depth in the slope were measured prior to and after the rainfall event, and data in two major rainfall events (accumulated precipitations with small and large amount) were presented. Major findings concluded from this research are: (1) the matric suctions of the soil at shallow depths in gullied slopes in dry season are significantly less than those in planar slopes and ridge-like slopes, and those in ridge-like slopes are slightly greater than those in planar slopes; (2) the amount of drop in the matric suctions of the soil in gullied slopes is considerably small compared with that in planar and ridge-like slopes; (3) after the rainfall event, the matric suctions of the soil at the shallow depth in the ridge-like slope are considerably greater than those in the planar and gullied slopes no matter what the amount of the accumulated precipitation is; (4) the influence of the rainfall with a low accumulated precipitation on the behavior of the matric suction of the soil in different slope terrains is similar to that with a high accumulated precipitation.