Permeability of Natural Clay Liners: Effect of Accelerated Permeability Testing on Soil Structure

A variety of clay specimens (Kaolin, Belfast Upper Boulder Clay and Belfast Sleech) were subjected to British Standards Triaxial Permeability Tests and Accelerated Permeability Tests in order to examine how the permeability predicted (under uniform effective stresses and conditions) varied depending on the testing method adopted. The specimens were then freeze-dried to preserve their post-test state, and examined using a Scanning Electron Microscope, in order to analyse their soil structure. In all cases the Accelerated Permeability Test predicted a value of permeability lower than that predicted by the British Standards Triaxial Permeability Test. Likewise, the soil structure present in the Accelerated Permeability Test specimens showed marked differences when compared to soil structure present in the British Standards Triaxial Permeability Test specimens; however the differences were not constant throughout the specimens. It was concluded that Accelerated Permeability Tests do result in soil structure degradation; however the full extent of this is not yet known. To ascertain this, it is recommended that a series of Accelerated Permeability and British Standards Triaxial Permeability Tests are performed on a variety of clays under varying effective stresses, along with a series of British Standards Uniaxial Compression Tests on these specimens post-test.