颗粒尺寸效应对高填方填料蠕变变形的影响机理研究

The size effect of rockfill materials is one of the main problems in creep behavior analysis of high-fill embankments. The creep deformation will be underestimated if the size effect of rockfill materials is ignored, which endangers the operation of high-fill geotechnical structures.This study will investigate the size effect of rockfill materials on the creep behavior of high-fill embankments in three scales—single particle, particle assemble and high fill structure.. Firstly, by means of uniaxial compression test, uniaxial creep test and acoustic emission test, the microscopic mechanism of size effect on rockfill particles with constant moisture content is revealed, and the relationship between acoustic emission parameters and damage variables considering size effect is established.. Secondly, the long-term properties of rockfill assembles are studied in the laboratory. Based on the results of laboratory tests, DEM models are generated to simulate the size effect of rockfill assembles, to explore the effect of particle size on the creep behavior of rockfill assembles and its mesoscopic mechanism, as well as to establish the relationship between particle breakage and creep deformation considering size effect.. Finally, a creep constitutive model is modified based on the relationship between particle size and creep deformation in order to consider the size effect. The numerical results based on the modified creep model are compared and validated with field monitoring data. The results of this study will provide certain scientific basis and technical support for accurately predicting and effectively controlling the creep deformation of the high-fill geotechnical structure.

填料尺寸效应是高填方地基蠕变变形分析的一个难题。忽略尺寸效应的影响将低估高填方的蠕变变形，给高填方土工构筑物的安全运营造成重大隐患。本项目针对高填方填料蠕变变形的尺寸效应，从高填方填料单颗粒、颗粒集合体以及高填方构筑物三个尺度展开研究。首先通过单颗粒尺寸效应试验、声发射试验、CT扫描，揭示尺寸效应对含水率恒定填料单颗粒力学特性影响的微观机理，提出考虑尺寸效应的单颗粒细观损伤关系式；然后，开展填料集合体蠕变变形尺寸效应室内试验，并以此为基础建立考虑尺寸效应影响的填料集合体离散元模型，研究颗粒尺寸对填料集合体蠕变变形的影响及其细观机理，建立考虑尺寸效应影响的颗粒破碎率与蠕变变形关系式；最后，基于尺寸效应对填料蠕变变形的影响，对现有的蠕变模型进行修改，使其考虑尺寸效应的影响，并与已有工程进行对比。研究结果将为高填方土工构筑物蠕变变形的预测和有效控制提供一些科学依据和技术支持。

蠕变变形是影响高填方土工构筑物长期运营安全的关键问题之一，而尺寸效应是影响高填方土工构筑物蠕变变形的一个重要因素。忽略尺寸效应的影响将低估填料的蠕变变形，给高填方土工构筑物的安全运营造成重大隐患。目前已有的研究工作对填料应力-应变-时间行为的尺寸效应考虑不够，对其微观机理认识不足，也缺乏相应的理论模型。本研究从我国高填方土工构筑物快速发展，对于高填方填筑材料应力-应变-时间行为的尺寸效应认识不足这一问题出发，耦合室内试验与数值模拟的研究手段，开展了如下研究：开展了不同尺寸试样的损伤特性的试验研究和数值模拟研究，得到了不同尺寸试样在单轴压缩和单轴蠕变试验条件下损伤演化规律，进而揭示了高填方填料单颗粒尺寸效应的微观机理；开展了不同颗粒尺寸填料集合体三轴压缩、固结蠕变室内试验和数值模拟试验，揭示了尺寸效应对填料集合体长期强度以及流变变形的影响机理。基于试验结果，修正已有的高填方填料流变模型，使其能够考虑尺寸效应的影响。研究的成果，能够为高填方土工构筑物的设计与施工提供一些科学依据。