The feasibility of mudstone material as a natural landfill liner

This paper presents the results of a series of laboratory tests investigating on physical properties and hydraulic conductive behaviors of a mudstone material obtained from southwestern Taiwan. The Atterberg limits and particle-size distribution examinations showed the liquid limit = 34.1%, the plasticity index = 15.2%, the percentage fines (< No. 200 sieve) ≤ 95.1%, the percentage of clay (< 2 μm) ≤ 30%, and the activity = 0.5. These characteristics perfectly satisfied the essential requirements for soil properties of landfill liner. Based on the column experiments using two different grain sizes of beads to simulate the mudstone liner constructed on the gravel and the sandy soil, the hydraulic conductivity ≤ 1 X 10^-7 cm/s could be achieved if the hydraulic gradient is less than 13.9 (gravel) and 17.8 (sand), respectively. However, the hydraulic conductivity rose with an increase in hydraulic gradient. It was attributed to the fine granular mudstone penetrated through the simulated beads and led to the fine granular mudstone that could not fill up the void of beads. Moreover, the results of permeability tests performed using the rigid-wall and flexible-wall permeameters revealed that all of the hydraulic conductivities were less than 1 X 10^-7 cm/s for the mudstone with water contents from 17% to 37% (rigid-wall) and 14% to 29% (flexible-wall). Thus, it was confidently expected that this mudstone material could be applied on landfill soil liner.