Spatial and Temporal Solutions of Vertical Displacement of Ground Surface Caused by Freezing Tunnel Construction Under Different Frost Heave Modes

To predict the ground vertical displacement caused by horizontal freezing tunnel construction more scientifically, based on the frost heave interaction mechanism and experimental phenomenon between the soil around the freezing pipe and stratum, two different frost heave modes of the frozen soil around the freezing pipe under the constraint of the stratum are proposed in this study. The movement law of the frozen front with time was obtained according to the heat conduction theory. Further, the uniform and non-uniform frost heave modes were deduced by combining the image method and superposition principle. The space-time prediction formula for the ground vertical displacement caused by multiple freezing pipes in the construction of a horizontal freezing tunnel was developed using MATLAB software. In combination with an engineering example, the theoretical solution was compared with the measured data. Moreover, the influence of the parameters on the tunnel buried depth, frozen wall thickness, and uneven frost heave was analyzed. The results demonstrated that the displacement distribution law calculated by different frost heave modes is basically similar to the measured value in the overall trend, and the measured value is between the theoretical value of the uniform and non-uniform frost heave modes, which proves the rationality of the proposed theoretical model. Furthermore, the maximum vertical displacement calculated by the uniform and non-uniform frost heave modes appears in the center of the tunnel. However, the vertical displacement peak value of the ground surface above the tunnel center under different frost heave modes is differs significantly. When the other parameters are the same and the tunnel is buried shallower, the surface frost heave displacement distribution is narrower and higher; the influence of the soil frost heave mode on the surface displacement distribution is greater; the frozen wall is thicker; the vertical displacement of the surface is larger; the constant of the uneven frost heave degree is larger; and the maximum vertical displacement of the surface is higher. To ensure the safe and stable implementation of the project according to the specific situation, different frost heave modes are proposed in this paper to predict the ground deformation caused by the construction of a horizontal freezing tunnel. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.