基于水热力三场耦合理论的寒区隧道冻害机理及防治措施研究

Based on the existed problems in the investigation of the frozen rock mechanics, the stress , the continuity and energy principles of the frozen rock mass are established by the traditional studying means of the porous and phase medium mechanics ,with the analysis of the equilibrium principle of the frozen rock unit and the deformation principle of the 3-phases in the frozen rocks, and it is formed the real Thermal-Moisture-Stress(TMS) coupled theoretical frames in the saturated frozen rocks which can consider the force interaction between the rock skeleton and ice particle, and the energy jump behaviors during the phasing-changing between ice and water. The TMS coupled numerical model is built by the Finite-Element Method(FEM) based on the proposed coupled model in saturated freezing rocks, and the TMS coupled analysis software system which can simulate the process of the freezing and thawing of the rock is built also, which is comprehensively checked and validated by a relevant chamber experiment. The freezing-thawing laboratory test and triaxial compression test are done with the samples from cold region tunnel in Northeast China.The failure forms，strength，deformation and degradation characteristics of rock under different freezing-thawing condition are analyzed. Based on the above researches，the damage mechanism is found to consider the freezing-thawing effete in rock and the damage constitutive model is presented to describe the rock-water-ice relationship of surrounding cold region tunnel .Finally, a real cold regions tunnel is analyzed by the TMS coupled analysis software above, and some measures which solve the frost heave are advanced in this project.

依据经典的多孔多相介质力学研究方法，建立以多孔多相介质的质量守恒方程、力学平衡方程与热、能守恒方程为基础的全面考虑冻结岩石中岩石介质、冰、水三相介质水、热、力与变形的真正耦合作用的控制微分方程理论框架，探索寒区隧道冻害发生的机理。从工程现场选取典型岩石，进行室内冻融循环和三轴压缩试验，分析试件变形破坏的规律，研究其应力应变关系，寻找抗压强度、弹性模量这些物理参数与温度及不同含水量之间的变化关系，同时对数值模型加以验证。应用三场耦合理论模型，对大型商业软件进行二次开发以及自主研发能模拟冻结岩石冻结与融化过程的三场耦合分析软件系统。利用室内试验所得参数，以东北地区的实际工程为依托，进行寒区隧道冻融过程的三场耦合数值仿真分析与防治措施探讨，提出解决寒区隧道冻害问题的合理手段。

本项目主要针对寒区隧道中存在的冻害问题展开微观机理及实际工程的数值分析研究。依据传统的多孔多相介质研究方法，在微观机理方面主要针对饱和冻结岩石和非饱和冻结岩石的温度场、水分场及应力场的三场耦合研究分析，最终建立了以多孔多相介质的能量守恒方程、力学平衡方程与控制微分方程，在理论上探讨了冻结岩石冻胀机理，通过研究发现，当冻结岩石由上到下冻结时，上部冻结岩石的温度较低，由于负温造成岩石对其周围未冻水的吸附力增大，从而引起温度较高处的未冻水向温度较低处迁移，并使得该处冻结岩石的体积膨胀；同时，该处的未冻水有一部分相变成冰，体积膨胀1.09倍，又使得该处的未冻水向外挤出。当岩石对其周围未冻水的吸附力大于该处水分由相变产生的挤压力时，就使得该处的冻结岩石产生冻胀；当从上部向下推移时，温度逐渐增高，岩石对其周围未冻水的吸附力减弱，有可能使得向该处迁移的水分不能弥补由于相变挤压而流出的水分，就不能产生冻胀，依据此我们可更深入的研究冻结岩石发生冻胀破坏的本质。在实际工程方面，本项目针对我国东北地区及西南地区的实际冻害问题，开展大量的数值试验研究，主要分析了隧道局部存水空间冻胀所产生的附加应力，存水部位在拱顶、边墙、拱脚和仰拱不同部位对隧道衬砌的影响；同时对东北冻土区和西南冻土区的不同长度、不同埋深、不同断面大小及不同气候条件下的隧道抗防冻范围进行了计算。从计算结果可以看出，隧道断面积和最大埋深对隧道的冻结长度影响显著。通过本项目的研究发现，从微观角度和宏观实际工程的研究都可发现，温度、含水量及围岩的物理力学性质对寒区隧道的冻胀破坏起着决定性的作用，这正切合了本项目立项的初衷，将寒区隧道水分场、温度场、应力场三场耦合作用同时考虑进去，才能真正探讨寒区隧道的冻害问题，当然由于时间的局限，本项目后续还将继续开展室内试验的补充研究以及关于岩石冻胀机理方面的深入探讨。