Altered geosynthetic clay liners: effect on the hydraulic performance of composite liners

Abstract

This study evaluates how alteration of geosynthetic clay liners (GCLs) affects the hydraulic behaviour of a composite liner when the geomembrane presenting a hole is overlying a GCL. Interface transmissivity experiments were performed on GCL specimens that were exhumed from field sites. The results reveal different trends in the flow rates, which decrease differently to their steady state values. The steady state flow rates obtained and the calculated interface transmissivities are of the same order of magnitude as results obtained with a virgin GCL. The transient flow rate results are discussed in relation with the GCLs parameters. Based on these results, a new equation is derived that links interface transmissivity to the hydraulic conductivity of GCLs that have been altered by the environment. Considering large transient flow rates in calculations result in a greater leakage volume penetrating the liner when compared to calculations of infiltrated volumes considering only steady state leakage volume for a period of time of 1, 10 or 30 years. From a practical point of view, this suggests the introduction of a factor of safety of 1.67 when calculating the flow rate in composite liners in order to take into account the alteration by the environment of GCLs.

Effect of the durability of GCLs on Contaminants transfer through a composite liner exhibiting a hole in the geomembrane: A numerical approach

“…Based on experimental flow rates, the same parametric procedure was used for selecting interface transmissivity. A study performed by [12] looked at flow rates for virgin and aged GCLs in conjunction with a GMB with a 4 mm hole. Results of this study are presented in table 1.…”

“…Compared to virgin GCL, these internal and external influences can significantly increase the hydraulic conductivity of GCL by 4 to 5 orders of magnitude depending on site conditions [11]. In spite of that, no significant increase in advective flow rate has been observed (less than one order of magnitude) [12].…”

Effects of Pore Fluid and Surface Roughness on Geomembrane - Soil Interface Behavior

“…This situation can be explained as follows, the notches of the textured GM and the soil particles are interlocked during shearing so that the shear stresses increase for a long time and then take a constant value. On the other hand, in a smooth geomembrane, the soil particles adhere to the GM surface for a while and then slide on the smooth surface, causing shear stresses to increase and then fixate [1,18,48]. Also, for two soil types, the soil -HDPE/T shear strength has been determined greater than the soil -HDPE shear strength.…”