The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-...The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-based barrier materials.However,the common assumption of perfectly flushing conditions at the specimen boundaries could induce errors in analyses of the diffusion coefficients and membrane efficiencies.In this study,an innovative pseudo three-dimensional(3D)analytical method was proposed to evaluate solute distribution along the boundary surfaces of the soil-porous disks system,considering the non-perfectly flushing conditions.The results were consistent with numerical models under two scenarios considering different inflow/outflow positions.The proposed model has been demonstrated to be an accurate and reliable method to estimate solute distributions along the bound-aries.The calculated membrane efficiency coefficient and diffusion coefficient based on the proposed analytical method are more accurate,resulting in up to 50%less relative error than the traditional approach that adopts the arithmetic mean value of the influent and effluent concentrations.The retar-dation factor of the clay specimen also can be calculated with a revised cumulative mass approach.Finally,the simulated transient solute transport matched with experimental data from a multi-stage through-diffusion and membrane behavior test,validating the accuracy of the proposed method.展开更多
A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to agg...A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to aggressive leachate conditions,the neglect of the chemical incompatibility of the GCL can potentially result in an underestimation of the leakage rate and flux through the composite liner.This paper proposed a numerical investigation on the effect of chemical incompatibility of GCL on the barrier performance of the composite liner with hole defect.Four cases with leachate solutions having varied cation valencies and ionic strengths were analyzed,in which the hydraulic conductivity of GCL was concentrationdependent.Both the effect of the chemical incompatibility of GCL and the mechanisms were analyzed.The incompatibility of GCL resulted in significant increases in leakage rate and flux through the composite liner by factors of up to 4.9 and 5.0,respectively.The incompatibility-affected area in GCL is located within 0.1 m from the center of the hole in the GMB.The coupled increase in the hydraulic conductivity of GCL and pore water concentration impacts the flux and leakage in a short period of time.With GCL chemical incompatibility considered,advection may dominate the contaminant transport through GCL.展开更多
基金The financial support received from the Ministry of Science and Technology of the People’s Republic of China(Grant No.2019YFC1806002)National Natural Science Foundation of China(Grant Nos.42107174,42077241)is gratefully acknowledged.
文摘The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-based barrier materials.However,the common assumption of perfectly flushing conditions at the specimen boundaries could induce errors in analyses of the diffusion coefficients and membrane efficiencies.In this study,an innovative pseudo three-dimensional(3D)analytical method was proposed to evaluate solute distribution along the boundary surfaces of the soil-porous disks system,considering the non-perfectly flushing conditions.The results were consistent with numerical models under two scenarios considering different inflow/outflow positions.The proposed model has been demonstrated to be an accurate and reliable method to estimate solute distributions along the bound-aries.The calculated membrane efficiency coefficient and diffusion coefficient based on the proposed analytical method are more accurate,resulting in up to 50%less relative error than the traditional approach that adopts the arithmetic mean value of the influent and effluent concentrations.The retar-dation factor of the clay specimen also can be calculated with a revised cumulative mass approach.Finally,the simulated transient solute transport matched with experimental data from a multi-stage through-diffusion and membrane behavior test,validating the accuracy of the proposed method.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC1802304 and 2019YFC1806002)the National Natural Science Foundation of China(Nos.42077241 and 51988101)。
文摘A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to aggressive leachate conditions,the neglect of the chemical incompatibility of the GCL can potentially result in an underestimation of the leakage rate and flux through the composite liner.This paper proposed a numerical investigation on the effect of chemical incompatibility of GCL on the barrier performance of the composite liner with hole defect.Four cases with leachate solutions having varied cation valencies and ionic strengths were analyzed,in which the hydraulic conductivity of GCL was concentrationdependent.Both the effect of the chemical incompatibility of GCL and the mechanisms were analyzed.The incompatibility of GCL resulted in significant increases in leakage rate and flux through the composite liner by factors of up to 4.9 and 5.0,respectively.The incompatibility-affected area in GCL is located within 0.1 m from the center of the hole in the GMB.The coupled increase in the hydraulic conductivity of GCL and pore water concentration impacts the flux and leakage in a short period of time.With GCL chemical incompatibility considered,advection may dominate the contaminant transport through GCL.
