基于CT 技术的冻融循环与荷载协同作用下混凝土材料的三维动态破损机制研究

In cold regions of west China, The together action of freeze-thaw and load is one of the main factors for leading to the damage of concrete. The dynamic damage of concrete-sort geotechnical materials mainly display in energy accumulation of internal defects and micro-crack propagation, coalescence and failure till the global instability process, while X-ray CT technique is an effective observation method for detecting non-destructively the internal meso–damage process of concrete. The meso fracture- damage process of concrete process were observed by using CT technology under The together action of freeze-thaw and load， Based on the meso-structure variation characteristics of concrete CT images，the 3D porous structure of concrete is reconstructed by means of full digital image processing analysis tools, the concrete pore space form、 pore development evolution process and the process of moisture migration in the pore was described. The dynamic damage process and the corresponding microstructure evolution law of quantitative description of concrete are established by Using the energy principle, the fractal theory, the interest area partition method , According to the results of CT test, the meso-structure in the process of evolution of concrete specimen is numerically simulated with meso-structure evolution and the macro-damage degradation constitutive model of concrete .So the new way is developed for the solution of concrete meso dynamic damage mechanism research and provides the theory basis for major engineering freeze-thaw catastrophe prediction and prevention research in the cold region.

在我国西部寒区，冻融循环与荷载协同作用往往是导致混凝土加速破坏的主要因素。其破损主要表现在材料内部初始缺陷能量积聚，微裂纹不断萌生，扩展、贯通直至整体失稳的过程，而X射线CT技术是无损探测混凝土内部细观破损过程的有效手段。项目应用CT技术对冻融循环协同荷载作用下的混凝土动态破损全过程进行追踪,通过获得混凝土细观结构变化图像对三维孔隙结构实现全数字化的的重建分析，描述冻融循环与荷载协同作用下混凝土孔隙的空间形态和孔隙发展演化过程以及水分在孔隙中迁移的过程。利用能量原理、分形理论、兴趣区域分区的方法建立协同作用下混凝土动态破损过程及相应细观结构演变规律的定量描述。并在CT试验的结果上，利用建立的细观结构演变与宏观损伤劣化的本构模型，进行冻融循环与荷载协同作用下混凝土试样破损过程中细观结构演变多尺度数值模拟, 开辟混凝土细观破损机理研究的新途径，为寒区重大工程冻融灾变预测提供较好的依据。

在我国西部寒区，冻融循环与荷载协同作用往往是导致混凝土加速破坏的主要因素。其破损主要表现在材料内部初始缺陷能量积聚，微裂纹不断萌生，扩展、贯通直至整体失稳的过程，而X射线CT技术是无损探测混凝土内部细观破损过程的有效手段。项目应用CT技术对冻融循环协同荷载作用下的混凝土动态破损全过程进行追踪,通过获得混凝土细观结构变化图像对三维孔隙结构实现全数字化的的重建分析，描述冻融循环与荷载协同作用下混凝土孔隙的空间形态和孔隙发展演化过程以及水分在孔隙中迁移的过程。利用能量原理、分形理论、兴趣区域分区的方法建立协同作用下混凝土动态破损过程及相应细观结构演变规律的定量描述。并在CT试验的结果上，利用建立的细观结构演变与宏观损伤劣化的本构模型，进行冻融循环与荷载协同作用下混凝土试样破损过程中细观结构演变多尺度数值模拟, 开辟混凝土细观破损机理研究的新途径，为寒区重大工程冻融灾变预测提供较好的依据。