Microscopic Study on Bentonite Component of Geosynthetic Clay Liners under Acidic Conditions

摘要

Geosynthetic clay liners (GCLs) are widely used in landfills and other engineering projects as waterproofing materials due to their low hydraulic conductivity, usually ＜ 5 × 10~(-11) m/s, when in contact with water. However, GCLs are now increasingly considered for their ability to contain mining leachates, and these leachates may cause an increase in their hydraulic conductivity. This study reports the fluid loss and hydraulic conductivity results of GCLs under acidic conditions and provides supportive evidence from scanning electron microscopy (SEM) and transmission electron microscopy (TEEM). Fluid loss and flexible-wall hydraulic conductivity tests were conducted on GCL samples and bentonite cake under different H_2SO_4 concentrations. SEM and TEM were conducted on the bentonite specimens from the fluid loss tests. Generally, the fluid loss and hydraulic conductivity increased with increasing acid concentration. SEM and TEM revealed differences in the natural micro-structures of bentonites and dissolution-induced re-arrangement of the clay microstructures when acids are applied. The observed changes could explain the experimental results and provide a reference for the application of GCLs under acidic conditions.