Applicability of the equivalent coefficient of permeability in geomembrane lining systems having defects

Several equations for estimating the quantities of leakage through geomembrane lining sys-tems with defects were proposed by Giroud (1989). The amount of seepage through the defects on the geomembranes underlain by low-permeability clay layers was described. When the geomembrane lining systems are modeled in the seepage analysis program for the cases with changing phreatic surfaces, equivalent coefficients of permeability representing leaking geomembrane lining systems are required. This parametric study on the equivalent coefficients of permeability with various thicknesses of lining soils and hydraulic depths shows that the equivalent coefficients of permeability on a representative hy-draulic depth can be used for the changing hydraulic head conditions within tolerable errors considering the uncertainties of underlying lining soil.