低温冻融条件下岩体温度-渗流-应力-损伤(THMD)耦合模型研究及其在寒区隧道中的应用

STUDY OF THERMO-HYDRO-MECHANICAL-DAMAGE(THMD) COUPLED MODEL IN THE CONDITION OF FREEZE-THAW CYCLES AND ITS APPLICATION TO COLD REGION TUNNELS

寒区隧道的围岩冻胀问题涉及到岩体温度场、渗流场、应力场以及冻融损伤相互作用的多场耦合问题。在THDM耦合机制分析基础上,基于连续介质力学、热力学、渗流力学、损伤力学以及分凝势理论,建立低温冻融条件下岩体THMD耦合模型。该模型不仅考虑体积应变对岩体温度场和渗流场的影响,温度梯度和渗透压力对岩体应力场的影响,还根据寒区工程实际,考虑冻胀压力和冻融循环对岩体劣化损伤的影响。数值仿真某寒区管道工程的冻胀过程,与现场的实测结果对比表明:该模型能很好地反映岩土体由于负温所产生的冻胀现象。在此基础上,分析极端气候条件下嘎隆拉隧道围岩冻胀力的变化规律,并对隧道在经历不同冻融循环次数后的变形和受力特征进行探讨。研究结果表明:极端气候条件下嘎隆拉隧道围岩的最大冻胀力达到1.6 MPa,冻融循环对隧道衬砌受力影响较大。

The frost heave of surrounding rock in cold regions tunnel involves the complicated interaction of temperature field, seepage field, stress field and freeze-thaw damage. Starting with the thermo-hydro-mechnical- damage（THMD） coupling mechanism analysis, based on the continuum mechanics, thermodynamics, the percolation mechanics, damage mechanics and points of segregation potential theory, a THMD coupled model under the condition of freeze-thaw cycles was established. The model not only considered the influence of volumetric strain on temperature field and seepage field, temperature gradient and seepage pressure on rock mass stress, but also, according to actual engineering, considered the influence of frost heave pressure and freeze-thaw cycles on the damage of rock mass. This model was applied to simulate the temperature and deformation of a pipeline engineering in cold region. By comparing with the in-situ monitoring data, it is found that the proposed model can reflect the frost heave phenomenon exactly. After that, a forecast about frost heave pressure of Galongla tunnel under extreme weather conditions was given, and the stress and deformation law after freeze-thaw cycles are obtained. From the calculation results, it is concluded that the maximum frost heave pressure can reach up to 1.6 MPa and the stress is increased greatly after freeze-thaw cycles.