Effect of Hydrostatic and Hydrodynamic Pressures on the Stability of Landfill Veneer Covers with an Internal Seeper
Publication: Journal of Hazardous, Toxic, and Radioactive Waste
Volume 27, Issue 3
Abstract
The accumulated water in the drainage layer of the municipal solid waste landfill veneer cover system becomes the principal cause of the failure of landfill cover. In this study, seismic stability evaluation is carried out using the pseudostatic approach considering direct sliding and uplifted floating failures. The factors of safety against direct sliding failure (FSds) and uplifted floating failure (FSuf) are estimated considering hydrostatic and hydrodynamic pressures. Hydrodynamic pressures acting along the failure planes are computed using Westergaard’s theory. The different cases based on the height of accumulated seepage levels in the drainage layer (hw) are considered in the analysis. The angle of the sliding plane (ψ) for direct sliding failure and the failure ratio (Ω) for the uplifted floating failure are evaluated to determine the critical values of FSds and FSuf. It is observed that the immersion ratio (Ir) is the most important parameter that significantly affects the factor of safety against both failure modes (FSds and FSuf) under seismic loading. The results of the present study under static loading are compared with the available results in the literature. The effects of the slope angle (θ), the ratio of the thickness of the cover soil layer to the height of the landfill (h/H), the stability number (c/γsatH), the horizontal seismic acceleration coefficient (kh), and the ratio of vertical to horizontal seismic acceleration coefficients (kv/kh) on FSds and FSuf are presented for different values of immersion ratios (Ir). The magnitude and the direction of seismic inertia forces also govern the factor of safety values against both direct sliding and uplifted floating failure modes. The design charts are established to estimate the allowable thickness of the cover soil layer (h) for different values of immersion ratios by targeting the factors of safety, FSds and FSuf ≥ 1.15. This condition ensures the safety of the landfill veneer cover system against direct sliding and uplifted floating failures simultaneously.
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Acknowledgments
Financial support for this project was provided by the Government of India, Ministry of Education (12-2/2019-U1), which is gratefully acknowledged.
Notation
The following symbols are used in this paper:
- AAct, APass
- area of active and passive wedges (m2);
- Af, Aaf
- area of failure and mass above the failure blocks (m2);
- Bf, Baf
- failure and mass above the failure blocks;
- c
- cohesion of the veneer cover soil (kPa);
- c0
- interface cohesion of the veneer cover soil (kPa);
- EA, EP
- interwedge forces (kN/m);
- FJR, FPJ
- normal forces from the soil acting on the sliding plane (kN/m);
- normal forces from the soil acting on the faces of the failure block (kN/m);
- FSds
- factor of safety against direct sliding failure (dimensionless);
- FSuf
- factor of safety against uplifted floating failure (dimensionless);
- h
- thickness of the cover soil slope (m);
- hw
- vertical height of accumulated water in the drainage layer (m);
- H
- height of the landfill (m);
- kh, kv
- horizontal and vertical seismic acceleration coefficients (dimensionless);
- Ir
- immersion ratio (dimensionless);
- lPJ, lJR
- lengths of the faces of the sliding plane (m);
- lPI
- length of the uplifted block (m);
- L
- length of the cover soil slope (m);
- N1, N2
- number of sections divided for ψmax and Ωmax;
- SPJ, SJR
- resisting forces against sliding failure acting on the sliding plane (kN/m);
- shear resisting forces acting on the faces of the failure block (kN/m);
- hydrostatic forces acting on the sliding plane for the case number x (kN/m);
- hydrodynamic forces acting on the sliding plane for the case number x (kN/m);
- hydrostatic forces acting on the faces of the failure block for the case number z (kN/m);
- hydrodynamic forces acting on the faces of the failure block for the case number z (kN/m);
- WAct, WPass
- weight of active and passive wedges (kN/m);
- Wf, Waf
- weight of failure and mass above the failure blocks (kN/m);
- γsat
- unit weight of the veneer cover soil under a saturated state (kN/m3);
- δ
- interface friction angle between the drainage layer and the cover soil layer above the drainage layer (°);
- ϕ
- angle of the internal friction of the veneer cover soil (°);
- θ
- slope angle of the veneer cover soil (°);
- ψ
- angle of the sliding plane “PJ” (°);
- ψmax
- maximum possible angle of the sliding plane “PJ” (°);
- ψcri
- critical angle of the sliding plane “PJ” (°);
- Ω
- failure ratio (dimensionless);
- Ωmax
- maximum possible failure ratio (dimensionless); and
- Ωn
- value of Ω at the nth section of Ωmax (dimensionless);.
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Received: Aug 5, 2022
Accepted: Jan 28, 2023
Published online: Mar 29, 2023
Published in print: Jul 1, 2023
Discussion open until: Aug 29, 2023
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