A Rigorous Approach to Enhance the Slope Stability of Coal Ash Embankments against Extreme Rainfall Events
Publication: International Journal of Geomechanics
Volume 24, Issue 11
Abstract
This study investigates the pore-water pressure increase associated with rainfall intensity and duration on a coal ash embankment slope and its effect on the slope stability for safe disposal and storage of coal ash storage facilities (CASFs). Several worldwide incidents during the last decades have revealed that rainfall-induced reductions in matric suction can compromise CASF slope stability, necessitating innovative solutions that address the influence of the coupled interplay of hydromechanical factors. For this reason, the key objective of the study is directed toward evaluating the efficacy of covers with capillary barrier effects (CCBE) to improve the stability of coal ash embankments. A comprehensive analysis, involving SEEP/W and SLOPE/W for uncoupled evaluations and SIGMA/W and SLOPE/W for coupled assessments, was conducted to explore various CCBE configurations. These configurations included fine coal ash (FCA)/coarse coal ash (CCA), FCA/fine recycled asphalt (FRA)/coarse recycled asphalt (CRA), and multilayered systems. The study also examined the influence of density, along with varying rainfall intensities and durations. Numerical modeling results suggest superior performance of three-layer systems, especially the FCA/FRA/CRA configuration, in maintaining matric suction and increasing the slope factor of safety. The system effectively relocated the point of maximum displacement away from the slope toe, suggesting a potential mechanism for enhanced stability and prevention of toe displacement failures. In addition, the study found that the performance of loose coal ash slopes improved with the application of passive reinforcement. The summarized research highlights a sustainable waste-covering-waste approach, introducing controlled nonhomogeneity in slopes to improve their stability against environmental factors.
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Data Availability Statement
Data generated or analyzed during this study are provided in full within the published article.
Notation
The following symbols are used in this paper:
- a, n, and m
- fitting parameters for the soil–water characteristic curve;
- c′ and ϕ′
- effective cohesion and the internal friction angle;
- Esat
- modulus of elasticity under saturated condition;
- Eunsat
- modulus of elasticity under unsaturated condition;
- F
- externally applied force;
- Fs
- factor of safety;
- Hc
- breakthrough head;
- [K]
- stiffness matrix;
- Kw and Ksat
- calculated and the measured saturated hydraulic conductivities;
- Kx and Ky
- hydraulic conductivity functions in the horizontal and vertical directions;
- [Ld]
- coupling matrix relating the displacements with water volume change;
- N
- maximum negative pore-water pressure;
- Pa
- atmospheric pressure (101.3 kPa);
- Q and H
- boundary influx and the applied pressure head;
- S
- degree of saturation;
- Sc
- slope of the soil–water characteristic curve;
- (ua − uw)
- matric suction;
- uw
- incremental pore-water pressure vector;
- α and β
- fitting parameters;
- γ and μ
- unit weight and Poisson's ratio;
- γw
- unit weight of the water;
- Δδ
- incremental deformation vector;
- θr
- residual volumetric water content;
- θw and θs
- soil volumetric water content and the saturated volumetric water content;
- Ψ
- total suction; and
- (σ − ua)
- net normal stress.
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Information & Authors
Information
Published In
International Journal of Geomechanics
Volume 24 • Issue 11 • November 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Feb 2, 2024
Accepted: May 30, 2024
Published online: Sep 5, 2024
Published in print: Nov 1, 2024
Discussion open until: Feb 5, 2025
ASCE Technical Topics:
- Ashes
- Climates
- Coal
- Energy engineering
- Energy sources (by type)
- Engineering materials (by type)
- Environmental engineering
- Fuels
- Geomechanics
- Geotechnical engineering
- Materials engineering
- Meteorology
- Mine wastes
- Non-renewable energy
- Pollutants
- Precipitation
- Rainfall
- Rainfall duration
- Rainfall intensity
- Slope stability
- Slopes
- Wastes
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