寒区隧道洞口冰碛层冻融损伤机理及其稳定性研究

The proposal of this project is aim to develop the freeze-thaw damage mechanism of moraine under the hydro-thermo-mechanical (THM) coupled conditions and its stability. Based on CT imaging technology, high-precision optical observation system, field exploration, laboratory tests , theoretical analysis and numerical calculation, a crack propagate model which can reveal the microstructure characterizes of moraine in the condition of freeze-thaw cycles or loads will established, the relationship between mesoscopic damage characteristic and macroscopic parameters will be developed to realize the expression of the hydro-thermo-mechanical macroscopic parameters. The frost heave force and its change law with the crack extension in the phase change of water → ice will be studied, a THM coupled model will proposed which can consider the influence of heat migration, crack extension and seepage change law of moraine with heterogeneous structural characteristics. The heaving damage mechanisms of moraine under the freeze-thaw conditions will be revealed, a heterogeneous numerical analysis model of moraine using automated cell machine ( CA) technology will be established, crack extension simulation will be realized by developing the large finite element software ABAQUS, the change law of the temperature , seepage and mechanical properties of surrounding rock will be analyzed, and the reasonable construction and insulation measures will be established to achieve the purposes of establishing guiding theory and method for engineering practice.

项目围绕温度-渗流-应力(THM)耦合条件下冰碛物的冻融损伤机理及其对隧道稳定性影响这一核心科学问题展开工作。以CT三维成像技术、高精度光学观测系统、现场监测、室内试验、理论分析和数值计算为手段，建立冻融循环及荷载作用下反映冰碛物材料的非均质细观结构特征的裂隙扩展模型，揭示细观损伤演化过程与宏观参数的协同特性，实现冰碛物水、热、力宏观参数非均质性表征；研究水→冰相变产生的冻胀力的大小及其随裂隙扩展变化规律，提出能够考虑冰碛物非均质结构特征的热量迁移、裂隙扩展和渗透性演化相互影响的THM耦合模型，揭示冻融条件下冰碛物冻胀破坏机制；采用自动细胞机（CA）技术，构建非均质冰碛物数值分析模型，通过二次开发大型有限元软件ABAQUS，实现裂隙动态扩展模拟与形迹预测，揭示冻融循环作用下隧道洞口温度场、渗流场及围岩力学性质变化规律，提出合理的施工及防寒保温措施，达到为工程实践建立指导性理论和方法的目的。

项目组围绕本项目研究计划和研究目标，通过室内试验、理论研究、数值分析和现场测试验证等手段， 主要开展了五个方面的研究。提出了一种能综合考虑岩石的整体完整性、孔隙率以及孔隙分布情况影响的岩石冻融损伤规律联合无损预测方法；利用立方体岩石材料中预制裂隙的方法，研究了含裂隙花岗岩试样在冻胀过程中变形随冻结温度和冻结时间变化的规律，揭示了冻胀变形的时空演化规律；结合弹性力学、断裂力学及流体力学相关理论，推导出裂隙岩体冻胀力理论演化模型；通过与现有研究结果对比验证了模型的正确性；利用MATLAB编制计算程序，通过二次开发大型有限元软件ABAQUS，提出了基于扩展有限元的数值分析方法。该方法可以很好的揭示出冻胀力作用下裂隙扩展过程中冻胀力的变化规律；依托西藏嘎隆拉隧道，提出了隧道温度场演化和冻胀力作用下的围岩劣化规律。