Thermal Behavior in Cross-Passage Construction during Artificial Ground Freezing: Case of Harbin Metro Line

The successful construction of cross passages in water-rich sand strata requires the ground reinforcement of soil in passage zones. To address these conditions, artificial ground freezing was introduced, which is an innovative presupport technique that has been extensively applied in tunnel engineering. However, insufficient temperature monitoring data and complex numerical models have hindered accurate predictions of complete freezing curtains in engineering applications. In light of this, this paper proposes a heat-moisture coupling model to predict the dynamic formation of the freezing curtain. This was achieved by combining the heat transfer, Richards's equation, and the Darcy equation for porous media. As a result, the hydraulic parameters could be obtained through nuclear magnetic resonance. The proposed numerical model was further validated through laboratory testing by applying various seepage flow conditions. Finally, a three-dimensional numerical model was established for the construction of cross passage during artificial freezing. To confirm the feasibility of the model, data from 53 points were continuously collected from the case study for more than 50 days. The proposed model delivers temperature results that are consistent with the field data.