An analytical solution for rainfall infiltration into an unsaturated infinite slope and its application to slope stability analysis

• Published in: International journal for numerical and analytical methods in geomechanics Vol. 37; no. 12; pp. 1737 - 1760
• Main Authors: Zhan, Tony L. T., Jia, G. W., Chen, Y.-M., Fredlund, D. G., Li, H.
• Format: Journal Article
• Language: English
• Published: Chichester Blackwell Publishing Ltd 25.08.2013; Wiley; Wiley Subscription Services, Inc
• Subjects: analytical solution; Applied sciences; Buildings. Public works; Computation methods. Tables. Charts; Computer simulation; Exact sciences and technology; Geotechnics; Infiltration; Mathematical analysis; Mathematical models; matric suction; Rainfall; rainfall infiltration; Slope stability; Soil mechanics. Rocks mechanics; Soils; Structural analysis. Stresses; surficial slope stability; Unsaturated; unsaturated soil slope; Water effect, drainage, ground water lowering, filtration; Water pressure; Suction; matric suction; Property of soil; Slope stability; analytical solution; surficial slope stability; Modeling; Soil mechanics; unsaturated soil slope; rainfall infiltration; Pore pressure; Analytical method; Rain water; Infiltration; Unsaturated soil
• ISSN: 0363-9061; 1096-9853
• DOI: 10.1002/nag.2106

SUMMARY Surficial slope failures in residual soils are common in tropical and subtropical regions as a result of rainfall infiltration. This study develops an analytical solution for simulating rainfall infiltration into an infinite unsaturated soil slope. The analytical solution is based on the general partial differential equation for water flow through unsaturated soils. It can accept soil–water characteristic curve and unsaturated permeability function of the exponential form into account. Numerical simulations are conducted to verify the assumptions of the analytical solution and demonstrate that the proposed analytical solution is acceptable for the coarse soils with low air entry values. The pore‐water pressure (pwp) distributions obtained from the analytical solution can be incorporated into a limit equilibrium method to do infinite slope stability analysis for a rain‐induced shallow slip. The analysis method takes into account the influence of the water content change on unit weight and hence on factor of safety. A series of analytical parametric analyses have been performed using the developed model. The analyses indicate that when the residual soil slope, consisting of a completely decomposed granite layer underlain by a less permeable layer, is subjected to a continuous heavy rainfall, the loss of negative pwp and the reduction in factor of safety were found to be most significant for the shallow soil layer and during the first 12 h. The antecedent and subsequent rainfall intensity, depth of a less permeable layer and slope angle all have a significant influence on the pwp response and hence the slope stability. Copyright © 2012 John Wiley & Sons, Ltd.