Influence of Fines Content on Stability of Unsaturated Soil Slopes

Natural sands usually consist of considerable fines content (FC) (various proportions of silt and/or clay), the presence of which significantly affects its structure and unsaturated behavior. Soil water characteristic curve (SWCC) is the primary and fundamental tool to address unsaturated soil properties as it relates to the soil suction and the soil water content. However, it is well accepted that the SWCC exhibits hysteresis as it does not follow the same path during desorption and sorption. For a constant value of suction, the soil water content in the desorption is always greater than in the sorption. SWCC considerably changes with the presence of fines in the soil. Therefore, the present study sheds some light on the unsaturated behavior of soil mixtures with varying FC. Ennore sand was reconstituted with various percentages of red soil fines to attain the desired proportions of the soil mixture. The degree of hysteresis between desorption and sorption is presented. The results revealed that increasing the FC in the soil significantly affects the degree of hysteresis. Furthermore, the effect of percentage fines and hysteretic SWCC on the unsaturated infinite slopes has been carried out. It is observed that there is a considerable difference in the factor of safety obtained for the various percentage of fines during sorption and desorption cycles. The present study emphasizes the significance of the influence of FC on the degree of hysteresis of SWCC as it affects slope stability significantly.