Evaluating the impact of bentonite granule size distribution and swelling on the hydraulic conductivity of geosynthetic clay liners

¹ School of Mechanics and Engineering Science, Shanghai Univ. Shanghai, 200444, PR China
² School of Civil Engineering, Qinghai University, Xining 810016, China
³ Wisconsin Distinguished Professor Emeritus, Geological Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA

^* Corresponding author: juanhou@staff.shu.edu.cn

Abstract

The impact of granular size, distribution, total intergranular porosity, mobile intergranular porosity, and the tortuosity of the flow paths on the hydraulic conductivity of geosynthetic clay liners (GCLs) was assessed using a COMSOL hydrodynamic model. Results showed that as the intergranular pore spaces become smaller as the bentonite granules swell, the hydraulic conductivity of the GCL decreases. This effect is more significant when the density of the bentonite is lower. Outcomes from the model also illustrate that flow in GCLs with low hydraulic conductivity occurs in fine pore spaces with a width on the order of 1 um. The mobile intergranular porosity through which flow occurs is approximately 0.05 after the bentonite swells, and is small relative to the total intergranular porosity. This indicates that most water within bentonite having low hydraulic conductivity is occluded within isolated pores. As the hydraulic conductivity decreases, the tortuosity of intergranular flow paths increases, varying from 1.38 to 1.03. The findings provide insight into the complex flow behavior in GCLs and factors that affect achieving low hydraulic conductivity.