交叠车站下穿段MJS+水平冻结冻胀位移场研究

交叠车站下穿段隧道进行开挖前首先要进行加固处理，以南京新建地铁7号线下穿既有10号线中胜站工程项目为背景，为控制施工引起既有运营车站的变形，采用MJS+水平冻结法联合加固方案。为掌握MJS+水平冻结联合加固的冻胀变形、冻胀位移场发展规律及其影响因素，进行冻胀位移场数值模拟。研究结果表明：在积极冻结过程中，“山”字形水泥土加固区内部及其左右两侧产生向上的变形，底部则产生向下的变形；水泥土加固区变形相比内外侧砂土变形较小，水泥土对抑制冻胀作用效果明显；地层初始温度越低，冻胀变形影响范围越广，变形值越大，在冻结40 d、地层初始温度为18℃时，既有车站底板在距中轴线水平距离12 m处产生最大冻胀变形，为6.97 mm,小于允许冻胀变形10 mm;在相同地层初始温度下，盐水温度越低，隧道埋深越浅，冻土帷幕越厚，冻胀产生的变形越大，实际工程中可通过优化盐水降温计划抑制冻胀变形以减小对周边环境的影响。研究结果可为相似工程提供设计参考理论依据。

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.