拱北隧道管幕冻结法温度场数值计算

以港珠澳大桥珠海连接段拱北隧道为工程实例,研究管幕冻结法的温度场发展规律,基于二维多孔介质传热理论,采用有限元软件COMSOL对积极冻结期的实际工况进行数值计算,模拟结果通过现场实测验证,研究了温度场在异形冻结管开启前后的发展与分布规律。结果表明:冻结30 d时,实顶管完全被冻土包裹,并且顶管之间开始形成连续的冻土帷幕;冻结50 d时,空顶管被冻土完全包裹;冻结90 d时,实顶管和空顶管处冻土帷幕厚度达到2.0 m,满足设计要求。在异形冻结管开启前、开启后10 d内和开启后10~20 d内,两顶管间中点处温度测点的平均温度变化速率分别为-0.86℃/d,-0.88℃/d和-0.25℃/d,之后各测点温度趋于稳定,进而形成温度较为均匀的冻土帷幕。研究成果可为类似冻结工程提供技术参考。

Numerical calculation of temperature field of freeze-sealing pipe roof method in Gongbei tunnel

This paper took the Gongbei tunnel in the Zhuhai Connection Section of the Hong Kong-Zhuhai-Macao Bridge as an example to study the development of the temperature field of the Freeze-Sealing Pipe Roof Method. Based on the heat transfer theory of two-dimensional porous media, the FEM software COMSOL was used to numerically analyze the actual working conditions of the active freezing period, the numerical calculation was verified by field measurement. The development and distribution of the temperature field before and after the opening of the special-shaped freezing pipes was studied. The results showed that: when freezing for 30 days, the concrete pipe was completely wrapped by frozen soil, and a continuous frozen soil curtain began to form between the concrete pipe and empty pipe, when freezing for 50 days, the empty pipe was completely wrapped by frozen soil, when freezing for 90 days, the thickness of the frozen soil curtain at the concrete pipe and the empty jacking pipe reached 2.0 m, which met the design requirements. The average temperature change rates of the temperature measurement point at the midpoint between the concrete pipe and empty pipe were -0.86 ℃/d, -0.88 ℃/d and -0.25 ℃/d before the opening of the special-shaped freezing pipes, within 10 days after opening and within 10-20 days after opening, respectively. After that, the temperature of each measuring point tended to be stable, thus forming a relatively uniform frozen soil curtain. The results could provide technical reference for similar projects in the future.