Effect of Hydrostatic and Hydrodynamic Pressures on the Stability of Landfill Veneer Covers with an Internal Seeper

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.