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针对软土地层中盾构地中对接冻结加固施工边界条件复杂、形成冻结壁体积小且形状不规则的特点,以上海地区某盾构对接冻结加固工程为原型,按照相似理论设计进行了冻结加固模型试验,分析了冻结过程中地层温度场的分布规律,获得以下结论:在盾构壳体内表面保温的条件下,冻结管内部冻土的平均发展速度是冻结管外部的1.5倍左右;冻结28 h后,冻结管内部冻结壁的温度分布基本稳定,盾构壳体与土体交接面的温度均处于-20℃左右,内部冻结壁的平均温度约为外部的1.9倍。在同圈冻结管的叠加作用下,冻结过程中冻结壁主面和界面的温度变化规律基本一致,仅在冻结初期有少许差别。在外圈冻结管的低温屏蔽作用下,内圈冻结管对外部土体基本不发挥冻结作用,在不同冻结管排间距及多根冻结管交叉冻结的情况下,冻结管外部的冻土扩展规律基本相同,仅两排冻结管之间的土体温度分布存在差别。研究结果表明,盾构地中对接冻结加固形成的冻结壁形状与外圈冻结管的布置形式相似,形成的冻结壁厚度及平均温度在冻结28 h后基本稳定。
In view of the complicated boundary conditions of butt-freezing and freezing in the shield tunnel in the soft ground, the frozen wall is small in volume and irregular in shape. Taking the shield freezing docking project in Shanghai as the prototype, the freezing and reinforcement are conducted according to the similar theoretical design Model test, the distribution law of the temperature field of the formation during the freezing process is analyzed, and the following conclusions are obtained: Under the conditions of heat preservation of the inner surface of the shield shell, the average development speed of the frozen soil inside the frozen pipe is about 1.5 times of that of the frozen pipe; h, the temperature distribution inside the freezing pipe is basically stable. The temperature of the interface between the shield shell and the soil is about -20 ℃, and the average temperature of the internal freezing wall is about 1.9 times of the outside. Under the superposition of frozen tubes in the same ring, the temperature variation of the main surface and the interface of the frozen wall in the freezing process are basically the same, with only a slight difference in the initial stage of freezing. Under the effect of cryogenic shield of the outer tube freezing tube, the inner tube freezing tube does not exert any freezing effect on the outer soil. Under the condition that the spacing of different tube rows and the freezing of multiple frozen tubes are frozen, the regularity of permafrost expansion outside the tube The same, only two rows of frozen soil temperature distribution between the different. The results show that the shape of the frozen wall formed by butting and freezing in the shield tunnel is similar to that of the frozen pipe in the outer ring, and the thickness and the average temperature of the frozen wall formed are basically stable after freezing for 28 h.