Investigation of Thermal Conductivity and Prediction Model of NAPL-Contaminated Saturated Soil

Abstract

Groundwater flowing through a nonaqueous-phase liquid (NAPL) source zone may generate large NAPL-contaminated saturated soils and act as a long-term source of soils and groundwater contamination. Remediation efficiency and cost are greatly influenced by an accurate prediction of the thermal conductivity of NAPL-contaminated saturated soils. In this work, a series of thermal conductivity tests were carried out using a thermal probe method to investigate the influencing factors together with the prediction model. The results show that the thermal conductivity of contaminated saturated soil versus NAPL content can be divided into three stages. The variation of the thermal conductivity with NAPL content shows a slow decrease in the first stage, a significant decrease in the second stage, and a more moderate decrease in the third stage. Based on the 53 complete mineral data of soils collected from the literature, the thermal conductivity of the solid particle equation was modified. It is confirmed that quartz content is a crucial factor influencing ks and cannot be replaced by sand content. Subsequently, a new model is proposed for the prediction of the thermal conductivity of contaminated saturated soil. To improve the prediction accuracy of the model, a new normalized thermal conductivity equation (ke) and a relationship of θ and ks/kl were proposed to modify the new model. After modification, the new model can provide a well-performing prediction for the thermal conductivity of NAPL-contaminated saturated soils.