Analysis of Rainfall-Caused Seepage into Underlying Bedrock Slope Based on Seepage Deformation Coupling
Publication: International Journal of Geomechanics
Volume 24, Issue 5
Abstract
Precipitation is one of the most important factors inducing shallow slope failures, and the shallow slope covering bedrocks is prone to instability after heavy rainfall. In one-dimensional (1D) seepage–deformation coupling issues, permeability coefficient and moisture vary with matric suction in unsaturated soil. Combining mass conservation, Darcy’s law, and elastic theory, an analytical solution for coupled seepage–deformation in unsaturated soil slopes during rainfall infiltration is derived using the Fourier integral transformation method. The analytical solution can be applied to a 1D seepage problem in a soil slope with flux at the top and impervious bedrock in the base under heavy precipitation, and is conducive to study infiltration into the slope under rainfall conditions. To validate the accuracy of the proposed analytical solution in this study, it is compared with monitored pore-water pressure data from the Gufenping Landslide in the red-bed region located in Nanjiang, Sichuan, China. The compared result shows a good consistency between the analytical solution and the measured results, with a minor relative error. Investigation of the parameters demonstrates that the water-level rise is closely related to the coupling, which is influenced by precipitation duration, precipitation intensity, soil properties, and slope angle. The bottom boundary of the slope is considered to be impermeable in this study, which leads to rainfall accumulation at the base over time, and the coupled effect becomes more pronounced at the bottom boundary.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The research reported in this paper was supported by the National Natural Science Foundation of China (Grant No. 42277183), the Chongqing Natural Science Innovation and Development Foundation (Grant No. CSTB2022NSCQ-LZX0044), and the Fundamental Research Funds for the Central Universities, CHD (Grant No. 300102262507).
Notation
The following symbols are used in this paper:
- c′
- effective cohesion;
- E
- elastic modulus on variation of net normal stresses;
- F
- elastic modulus linked with soil matric suction;
- Fs
- safety factor;
- g
- acceleration due to gravity;
- H*
- vertical thickness of partial saturated soil layer;
- h
- pressure head;
- h0
- initial pressure head;
- ks
- permeability coefficient linked with soil matric suction;
- L
- length of soil layer;
- n
- porosity of unsaturated soil;
- q
- rainfall intensity;
- Sr
- degree of saturation;
- t
- rainfall duration;
- u
- pore-water pressure;
- z
- depth of slope;
- α
- desaturation coefficient;
- αc
- coefficient of Biot’s hydromechanical coupling;
- β
- angle of slope;
- βw
- compressibility of fluid;
- γ
- total weight of unsaturated soil.;
- γw
- bulk density of water;
- ɛv
- soil overall volumetric strain;
- θ
- volumetric moisture;
- θr
- volumetric moisture at residual moisture content;
- θs
- volumetric moisture at full saturation;
- ρs
- soil density;
- ρw
- water density;
- ϕ′
- effective friction angle of unsaturated soils; and
- ϕb
- angle relating increase in shear strength to matric suction.
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International Journal of Geomechanics
Volume 24 • Issue 5 • May 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Apr 30, 2023
Accepted: Nov 7, 2023
Published online: Mar 7, 2024
Published in print: May 1, 2024
Discussion open until: Aug 7, 2024
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