Stability analysis of unsaturated soil slope during rainfall infiltration using coupled liquid-gas-solid three-phase model

• Published in: Water Science and Engineering Vol. 9; no. 3; pp. 183 - 194
• Main Authors: Sun, Dong-mei, Li, Xiao-min, Feng, Ping, Zang, Yong-ge
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2016; State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China; Elsevier
• Subjects: Coupled; Coupled liquid-gas-solid three-phase model; infiltration; liquid-gas-solid; Pore-air; Pore-air pressure; pressure; Rainfall; Rainfall infiltration; slope; soil; stability; three-phase; Unsaturated; Unsaturated soil slope stability; Pore-air pressure; Unsaturated soil slope stability; Rainfall infiltration; Coupled liquid-gas-solid three-phase model
• ISSN: 1674-2370; 2405-8106; 2405-8106
• DOI: 10.1016/j.wse.2016.06.008

Generally, most soil slope failures are induced by rainfall infiltration, a process that involves interactions between the liquid phase, gas phase,and solid skeleton in an unsaturated soil slope. In this study, a loosely coupled liquid-gas-solid three-phase model, linking two numerical codes,TOUGH2/EOS3, which is used for water-air two-phase flow analysis, and FLAC3D, which is used for mechanical analysis, was established. Themodel was validated through a documented water drainage experiment over a sandy column and a comparison of the results with measured dataand simulated results from other researchers. The proposed model was used to investigate the features of water-air two-phase flow and stressfields in an unsaturated soil slope during rainfall infiltration. The slope stability analysis was then performed based on the simulated water-airtwo-phase seepage and stress fields on a given slip surface. The results show that the safety factor for the given slip surface decreases first, thenincreases, and later decreases until the rainfall stops. Subsequently, a sudden rise occurs. After that, the safety factor decreases continually andreaches its lowest value, and then increases slowly to a steady value. The lowest value does not occur when the rainfall stops, indicating adelayed effect of the safety factor. The variations of the safety factor for the given slip surface are therefore caused by a combination of pore-airpressure, matric suction, normal stress, and net normal stress.