Study on MJS + Horizontal Freezing Frost Heave Displacement Field in Crossing Section of Overlapping Station

The tunnel must be strengthened first before the excavation of the tunnel at the crossing station. Based on the Nanjing New Metro Line 7 crossing the existing Line 10 Zhongsheng Station project, the MJS + horizontal freezing method for joint reinforcement scheme is adopted to control the deformation of the existing operating station caused by construction. Numerical simulation of frost heave displacement field was performed to grasp the evolution law and influencing factors of the frost heave deformation ad frost heave displacement field during MJS + horizontal freezing joint reinforcement. Research indicates: during the active freeze, the shape of the “mountain”-shaped cement and soil reinforced area is deformed upwards and the bottom is deformed downward; The deformation of the cement-reinforced area is smaller than that of the inner and outer sand, and the effect of the cement soil on the suppression of frost heave is obvious; the lower the initial formation temperature, the wider the range of frost heave deformation, and the larger the deformation value, when frozen for 40 days and the initial formation temperature is 18 ℃, the maximum frost heave at the existing station floor at a horizontal distance of 12 m from the central axis is 6.97 mm, less than the allowed 10 mm frost heave deformation; At the same initial formation temperature, the lower the brine temperature, the shallower the tunnel burial depth, the thicker the frozen soil curtain, and the larger the deformation caused by frost heave, in actual engineering, the frost heave deformation can be suppressed by optimizing the brine cooling plan to reduce the impact on the surrounding environment. The research results can provide design references and theoretical justifications for similar projects in the future.