A NUMERICAL MODEL FOR THERMAL CONDUCTIVITY OF SOFT SOILS BASED ON MESOSCOPIC SIMULATION

Thermal environment control is a powerful guarantee for the safe operation of utility tunnel. A precise estimation for soil thermal conductivity is just the critical basis for the thermal load of environment control system in underground space. Soft soils are very common in the development of underground space, especially in highly urbanized areas. Most available studies on soil thermal conductivity focus on the range of low and intermediate water content, but there is rarely a model suitable for unsaturated soft soils with high water content. Based on mesoscopic simulation, a numerical model is proposed in the present study for unsaturated soft soils with high water content. This model can include traditional factors like water content and dry density. It also can reveal the influence of mineralogy and particle size. Finally, the numerical model is validated by the experimental data of 20 soil samples in Su-Tong GIL utility tunnel project. The mineralogy composition and particle size distribution are measured in advance from X-ray diffraction analysis and laser particle size analyzer, from which the model parameters are derived and then the effective thermal conductivity can be reached by mesoscopic simulation of heat conduction. Results show that the values of most the modelled thermal conductivity are located within the±20%ranges of experimental data, which verifies the reliability of the numerical model in the present study. In the same time, it indicates that this numerical model has a potential application in predicting the thermal conductivity of unsaturated soft soils. Besides, this model can give a direct exhibition of local heat flux in soils, which lays a foundation for a better understanding on the mechanism of soil thermal behavior. The results in the present study can provide a new strategy and/or approach to estimate soils thermal conductivity.