Assessment of Heat Transfer‐Induced Contaminant Transport for a GMB/GCL/CCL Liner System

This paper presents a numerical investigation for full transient coupled heat transfer and contaminant transport in a landfill bottom liner system consisting of a geomembrane (GMB), a geosynthetic clay liner (GCL), and a compacted clay liner (CCL), considering the effect of three‐phases in saturated soil (i.e., solid particles, mobile pore fluid, and immobile pore fluid). Effects of effective porosity, GMB defects and wrinkles, and temperature‐induced changes in effective molecular diffusion coefficient, permeability coefficient, and distribution coefficient are considered. The proposed numerical solution is verified by comparing against the available analytical solutions, experimental results, and numerical model. Using the verified solution, simulations are performed to evaluate the effects of the temperature at the top boundary, GMB defects, GCL permeability, effective porosity of the GCL and CCL, and CCL thickness on contaminant transport. All the simulation results indicate that, regardless of the range of parameter values, heat transfer has a significant impact on contaminant transport through the GMB/GCL/CCL liner system, not only during the period of heat transfer but also decades after heat transfer is complete. For the condition considered in this study, neglecting the effect of heat transfer can underestimate the cumulative contaminant mass outflow by at least 1.487 times and, therefore, may lead to unconservative liner design and adverse environmental impacts.