Geotechnical characterization of peat-based landfill cover materials

Natural methane （CH4） oxidation that is carried out through the use of landfill covers （biocovers） is a promising method for reducing CH4 emissions from landfills. Previous studies on peat-based landfill covers have mainly focused on their biochemical properties （e.g. CH4 oxidation capacity）. However, the utilization of peat as a cover material also requires a solid understanding of its geotechnical properties （thermal, hydraulic, and mechanical）, which are critical to the performance of any biocover. Therefore, the objective of this context is to investigate and assess the geotechnical properties of peat-based cover materials （peat, peat–sand mixture）, including compaction, consolidation, and hydraulic and thermal conductivities. The studied materials show high compressibility to the increase of vertical stress, with compression index （Cc） values ranging from 0.16 to 0.358. The compressibility is a function of sand content such that the peat–sand mixture （1：3） has the lowest Cc value. Both the thermal and hydraulic conductivities are functions of moisture content, dry density, and sand content. The hydraulic conductivity varies from 1.74 × 10^-9 m/s to 7.35 × 10^-9 m/s, and increases with the increase in sand content. The thermal conductivity of the studied samples varies between 0.54 W/（m K） and 1.41 W/（m K） and it increases with the increases in moisture and sand contents. Increases in sand content generally increase the mechanical behavior of peat-based covers; however, they also cause relatively high hydraulic and thermal conductivities which are not favored properties for biocovers.