A theoretical thermal conductivity model for soils treated with microbially induced calcite precipitation (MICP)

Soil thermal conductivity is a predominant factor affecting the efficiency of exploitation of geothermal energy. Microbially induced calcite precipitation (MICP) technology has been proved to be effective in improving soil thermal conductivity. However, there is still a lack of a thermal conductivity prediction model for MICP treated soils. In this study, a theoretical thermal conductivity prediction model was developed based on the heat conduction theory and a simplified 2D geometric soil unit. The performance of this model was evaluated using the measured thermal conductivity in published literature. The results show that the predicted soil thermal conductivity agrees with the measured values well, especially, when the soil saturation (water content of the soil) is greater than 0.1. We analyze the influencing factors of soil thermal conductivity after MICP treatment on micro-scale. The results show that the soil thermal conductivity increases nonlinearly with the ratio of cement radius to soil particle radius, beta. For example, the thermal conductivity can be increased by more than 16 times from 0.25 W/(m K) to 4.14 W/(m K) when beta increases from 0 is 0.8, if the ratio of soil particle spacing to soil particle radius 4 is zero. 4 is also found to have a significant influence on soil thermal conductivity. For example, the soil thermal conductivity increases by 0.19 W/(m K) and 1.08 W/(m K) in dry and saturated states, respectively, when xi increases from 0 to 0.33. This theoretical thermal conductivity model will provide a great calculation method for the soil thermal conductivity after MICP treatment. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A theoretical thermal conductivity prediction model was developed for MICP treated soils, showing that soil thermal conductivity increases nonlinearly with the ratio of cement radius to soil particle radius and soil particle spacing to soil particle radius. The model provides a calculation method for predicting soil thermal conductivity after MICP treatment.