Three-dimensional deformation of strata that are rich with water during construction of a plane skew connecting channel using artificial ground freezing technique

Artificial ground freezing technology empowering the construction of urban subway tunnels has been recognized as one of the most environmentally, friendly and efficient construction methods. However, ground frost heave and thaw settlement are the primary issues to be addressed in engineering practice, and anticipating these issues in advance will bring tremendous assistance to the construction of subway tunnels. Therefore, a three-dimensional thermodynamic coupling method is derived considering the phase transition process and the anisotropic characteristics of freeze-thaw soil. By calling the compiled incremental matrix equation in ABAQUS, the whole process simulation of the freezing construction of a plane skew connecting channel of Fuzhou Metro Line 5 is realized. The numerical simulation results indicate that the evolution process of the freezing temperature field and thawing temperature field in numerical simulation is consistent with the theoretical design, and the natural thawing time is about 1.5 times of the positive freezing time. Besides, the evolution law of ground surface displacement in numerical simulation is consistent with the field measurement, and their displacement-time curves conform to the power function fitting relationship, and the correlation coefficients are all greater than 0.9. After freezing for 45 days, the ground surface frost heave displacement at the midpoint of the connecting channel in numerical simulation is 52.43 mm, while the measured value on site is 49.58 mm, with an error of only 2.85 mm. After thawing for 68 days, the ground surface thaw settlement displacement at the midpoint of the connecting channel in numerical simulation is - 23.77 mm, while the measured value on site is - 24.02 mm, with an error of only 0.25 mm. All these indicate the accuracy of the established numerical simulation prediction method.