A saturation-normalized thermal conductivity framework for municipal solid waste with composition-related differences...

Thermal conductivity is important for landfill temperature evolution and thermal safety assessment. Moisture is generally regarded as the main factor controlling thermal conductivity in municipal solid waste (MSW), but the role of composition in shifting conductivity bounds and shaping unsaturated response remains unclear. In this study, thermal conductivity was measured at 20-23 °C using a transient thermal probe for four aged MSW samples with approximate landfill ages of 5, 10, 15, and 20 years and one fresh MSW sample based on typical Wuhan MSW composition. Specimens were prepared at target dry densities of 400-700 kg·m^-3 under dry, saturated, and unsaturated conditions. Unsaturated specimens had volumetric water contents of 25.86-62.14% and saturation of 0.328-0.957. Dry-state thermal conductivity ranged from 0.0304 to 0.0616 W·m^-1·K^-1, while saturated values from 0.4735 to 0.7211 W·m^-1·K^-1. Under unsaturated conditions, thermal conductivity generally increased with moisture level, with sample-dependent variations. Saturation showed a slightly stronger association with thermal conductivity than volumetric water content. Among three candidate K_e-S_r formulations, the Côté & Konrad model performed best, with grouped fitting outperforming full-data fitting. Waste components were regrouped as rigid mineral skeleton, flexible low-thermal-conductivity barrier, and hydrophilic/biodegradable bridging components to interpret sample differences. The results suggest that skeleton-dominated components are more closely related to sustained heat transfer at medium to high saturation, whereas hydrophilic/biodegradable components mainly affect the early heat-transfer development at low saturation. The saturation-normalized framework supports estimating MSW thermal conductivity and interpreting composition-related differences in unsaturated response.