Determination of water content of a residual soil slope in response to infiltrating rainwater using transient seepage model and its verification

• Published in: Wārasān Songkhlā Nakharin 2021-12, Vol.43 (6), p.1701-1707
• Main Authors: Thitinan Indhanu, Panupong Thumtuan, Tanan Chub-Uppakarn, Tanit Chalermyanont
• Format: Article
• Language: English
• Subjects: pore water pressure; residual soil slope; transient seepage model; volumetric water content
• ISSN: 0125-3395
• DOI: 10.14456/sjst-psu.2021.223

Reduction of soil shear strength is significant in evaluating slope failure for rainfall-induced landslide study. Increasing soil water content due to infiltrating rainwater increases pore water pressure and decreases the shear strength of soil. In this paper, transient seepage simulations were conducted to determine the change of pore water pressure and water content of the soil in a test pit in response to rainfall. Simulation results were verified by comparing to field monitoring data recorded from time domain reflectometers installed in the test pit. Simulation results showed that the topsoil solely responded to the rain as its pore water pressure promptly changed from negative to positive indicating that the infiltrating rainwater had changed the soil from unsaturated to saturated soil. For deeper soils, due to their low permeability, their pore water pressures slightly increased as the water in the topsoil marginally flowed downward but it mostly drained downslope to slope toe. The simulated volumetric water content compared fairly well to the observed one as percent errors were lower than 10 percent.