隧道冷板冻结温度场数值模型构建及分析

Modeling and Analysis of Temperature Field of Tunnel Concrete Structure with Cold Plates

  • 摘要: 冻结法施工中,在混凝土结构表面外敷冷板是提高隧道冻结效果的常用方法。文章以广州地铁广佛线某区间冻结封水工程施工为背景,在现有理论研究成果的基础上,采用Ansys软件建立了隧道冷板冻结温度场数值计算模型,分析了影响冻结温度场的各个因素,结果表明:1)冻结主面、界面上温度随深度的分布曲线为对数曲线形式,冻结初期主界面上温差很大,随冻结时间的延长,主界面温度相差不大;2)管片与土体交界面上的温度分布曲线在冷源附近为抛物线形,远处逐渐过渡为平缓曲线;3)在冷板间距较小的情况下,由于双冷板叠加作用,冻结10 d后界面上温度明显低于主面上温度,界面上冻结效果优于主面。冻结40 d后,降温速度明显变缓,冻结范围增长较小;4)在其它参数不变的情况下,存在一个最优冷板布置间距,使界面上冻土壁厚度达到最大。

     

    Abstract: It is common to lay a cold plate on the concrete structure to improve freezing effect during tunnel con? struction by freezing method. Taking a water blocking project by freezing method on Guangzhou-Foshan line of Guangzhou metro for example, a numerical calculation model of temperature field regarding the cold plate applied on the tunnel structure was established with Ansys software based on existing theoretic researches, and the factors affecting freezing temperature field were analyzed. The results show that the distribution curves of temperatures on main face and interface of frozen wall varying with depth are of the logarithmic curve form, the temperature difference on the main face is large at the first freezing stage and it becomes small with the time of freezing; the temperature distribution curve on the interface between segment and soil mass near the cold source is of the parabolic form and it gradually transits to a flat curve in the distance; the temperature on the interface is obviously lower than that on main freezing face after ten days of freezing in the case of small interval of cold plates due to superposition of double cold plates, and the freezing effect of the interface is better than that of the main face. The cooling rate significantly slows down and the increase of freezing scope is small after 40 days of freezing; there is an optimal interval for cold plates in the case of keeping all parameters unchanged, which makes the frozen wall thickness on the interface being maximum.

     

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