基于热流固耦合的寒区隧道冻害机理与区段分类研究

For the tunnels in cold region when considering the life-cycle safety, the mechanism of frost damage and the corresponding control measures are the significant technical and theoretical issues. Facing the contradiction of the increment of tunnels in cold region and the increase of frost damage, the ice damage mechanism and the control measures will be systematically studied in this proposal. The analysis is based on large amount of practical projects and performed utilizing theoretical analysis, model test, numerical simulation and in situ tests. Through evaluating the frost heaving force and the freezing body, based upon the transmission of heat among gas, liquid and solid tri-state mediums, and considering the flow process of underground water from surrounding rock to the outside of tunnel, the fluid-solid-heat coupling model can be reached and include the phase change and the influence of turbulence. The numerical solution of the coupling model can be obtained by utilizing program compiling. Based upon the model test and large amount of computation, the internal relation of the frost heaving force and the freezing body with respect to the four kinds of factors can been analyzed, which are the meteorological environment, the geological environment, the hydrologic environment and engineering measures. Therefore, the mechanism of frost damage can be achieved. Employing the factor analysis method, the sensitivity and the influence degree of the four types of factors can be studied. Upon the systematic analysis of on-site frost damage cases in tunnel, from the perspective of the temperature field with three states, the method and the standard for scientific sectionalized classification can be formed, which will lay the foundation for choosing the countermeasures for tunnels in cold region. The outcomes of this proposal can play significant role for the design, the construction, and the maintenance of tunnels in cold regions.

冻害发生机理与防控是寒区隧道工程全寿命期的重大理论和技术难题，面对寒区隧道数量增加与冻害频发的矛盾，本课题以冻胀力和结冰体作为评判指标，依托大量工程实践，采用理论分析、模型试验、数值仿真和现场测试等手段，从热量在固、液、气三态物质间的多方式传递角度，考虑地下水由围岩经排水系统到洞外的流动全过程，构建含相变和紊流影响的热-流-固耦合模型；采用程序编译手段完成耦合模型的数值求解，基于相似模型试验和海量计算，发现气象环境、地质环境、水文环境和工程措施四类因素集与冻胀力和结冰体两个指标间的内在关系，揭示寒区隧道冻害发生机理。采用因素分析法对四类因素集中各因素的敏感度和影响度进行研究，系统分析现场隧道冻害案例，从三态物质的温度场角度形成科学可行的寒区隧道区段分类方法和分类标准，为寒区隧道冻害防控对策的选择奠定基础。研究成果对于寒区隧道的抗防冻设计、施工和维修养护具有重要理论意义和工程实用价值。

我国的疆域幅员辽阔，其中寒冷区域分布广泛，主要以北部高纬度和西部高海拔地区为代表。伴随中西部协调发展和振兴东北等战略的推进，寒冷地区的交通基础设施建设发展迅猛，隧道工程作为克服地形障碍的主要形式，数量猛增。鉴于前期对寒区隧道抗防冻的认识不足，导致既有寒区隧道工程冻害问题日益突出。着眼于寒区隧道工程的冻害防控理论和技术，课题组重点开展了寒区隧道冻害发生模型、冻害影响因素与规律、冻害发生机理和冻害防控技术体系等方面的研究工作，一定程度上推动了寒区隧道工程领域进展，得到了一定的研究成果：（1）在考虑紊流等效应的基础上，建立了适用于寒区隧道冻害防控的热流固耦合计算模型，经过多座寒区隧道现场实测数据的验证表明模型具有良好的可靠性；（2）明晰了气象条件（气温、风速、风向等）、地质条件（导热系数、比热容、密度等）、工程措施（保温层、排水沟、纵向设防段落）等诸多因素对寒区隧道冻害发生、发展和后果的影响规律，揭示了寒区隧道工程的冻害发生机理；（3）建立了基于耦合温度场的寒区隧道分类方法，确定了气温主导型、地温主导型和水温主导型三个主要类型，并分别形成了相应的寒区隧道冻害防控技术体系，特别是确定了寒区隧道深埋中心水沟合理埋置深度、纵向设防长度、保温层设计参数三个关键抗防冻措施的设计计算方法，并成功应用于京沈、辽中环线等多个隧道工程。工程应用结果表明，相关计算方法简单易用，具有良好的可靠性，可以为寒区隧道冻害防控提供良好的理论支持，对于需求日益迫切的新建寒区隧道和数量庞大的既有寒区隧道而言，具有良好的工程科学价值和推广应用前景。