海底隧道管幕冻结法水热耦合温度场数值模拟分析

Numerical Simulation Analysis of Hydrothermal Coupling Temperature Field of Pipe Curtain Freezing Method in Submarine Tunnel

为得到渗流作用下管幕冻结法温度场的发展规律,结合三亚河口通道隧道冻结工程,基于达西定律与多孔介质传热理论,运用有限元软件建立水热耦合数值模型,采用更改模型渗流流速大小和建立测温路径的方法,围绕冻土帷幕的发展情况、交圈时间、壁厚进行分析。结果表明,冻土帷幕随渗流的流向发展,下游侧土体开始冻结的时间早于上游侧土体,且最终温度低于上游侧土体;当流速约为2.87 m/d时,低渗流流速作用对整体冻土帷幕交圈的时间影响较小;随着渗流流速的增大,整体冻土帷幕交圈所需的时间明显增加,其区域的不均匀程度变大,厚度减小;当流速增大至约10.02 m/d时,冻土帷幕出现局部不交圈的情况。考虑到原冻结方案偏于保守,设计优化方案为将内圈冻结管总数由80根减少至56根,模拟分析后的平均冻土帷幕厚度约为4.28 m,相较于原方案减少了0.195 m,仍满足冻结设计要求。

To investigate the development of temperature fields under seepage conditions for pipe curtain freezing method,draw⁃ing on the Sanya River Estuary Trench Tunnel freezing project,combined with Darcy′s law and heat transfer theory in porous media,using finite element software to establish a coupled water-heat numerical model,the study employs varying seepage rates in the model and a method for creating temperature measurement paths,and analyzes the evolution of the frozen soil curtain,circulation time,and wall thickness.The results indicate that the frozen soil curtain develops along the seepage direction,with the soil on the downstream side freezing earlier than the upstream side,and attaining a lower final temperature;when the flow rate is approximately 2.87 m/d,the impact of low seepage rates on the overall circulation time of the frozen soil curtain is relatively minor;as the seepage rate in⁃creases,the overall circulation time of the frozen soil curtain grows significantly,accompanied by increased regional unevenness and a decrease in thickness;when the flow rate increases to approximately 10.02 m/d,local non-circulation occurs in the frozen soil cur⁃tain.Considering the original freezing plan to be conservative,an optimized design is proposed:reducing the number of inner circle freezing pipes from 80 to 56,the simulated average thickness of the frozen soil curtain is approximately 4.28 m,a decrease of 0.195 m compared to the original plan.This optimized design still meets the freezing design specifications.