Optimal reliability based design of V-shaped anchor trenches for MSW landfills

Geomembrane liners that are installed in anchor trenches may experience pullout failure when the applied tensile stress exceeds the allowable strength of the liner. Deterministic analysis approaches do not consider the variability of the unit weight and friction angle of the soil, interface friction between the geomembrane and the cover soil, and tensile strength of the geomembrane. An analytical expression based on the Euler-Eytelwein equation is derived for the mobilized tension in the anchor. This paper proposes a new procedure for the target reliability-based design optimization (TRBDO) of V-shaped anchor trenches. The effect of the bend resistance on the GMB tensile force and reliability index is discussed. This approach is used to determine an optimal allowable geomembrane tensile force required to avoid pullout failure such that the prescribed reliability indices are attained in the presence of parameter variability. The optimization methodology is useful to develop modifications for conventional analytical models in practice. Thus, the proposed procedure combines modern concepts of reliability analysis, anchor trench design, and nonlinear constrained optimization to develop a rational and practical procedure for the optimal design of V-shaped anchor trenches.