This paper proposes a modelling approach that combines the discrete element method (DEM) and a novel bonded contact model to characterise the fatigue response of cemented materials. While DEM is commonly used to simulate bonded materials undergoing cracking, the centrepiece of the present method is the development of the novel bonded fatigue model. This new model couples damage mechanics and bounding surface plasticity theory to capture fatigue crack growth in cement bridges between aggregates. Thanks to the incorporation of the bounding surface plasticity, the proposed model provides a smooth transition from static to fatigue damages and vice-versa in a unified manner, making it more flexible to capture damage responses of cemented materials under different loading conditions (i.e. monotonic and cyclic loadings). Moreover, the proposed approach automatically captures the hysteretic response in cement bridges between aggregates under fatigue loadings without ad-hoc treatments. More importantly, by removing the direct dependence of the fatigue damage variable on the number of loading cycles, the modelling approach can be applied to simulate the fatigue behaviour of cemented materials under cyclic variable load amplitudes. The proposed modelling approach is evaluated against several strength tests to examine its predictive capability. Satisfactory agreements with fatigue experiments are achieved for flexural modulus degradations, lifetimes and sensitivity of stress levels under constant and variable amplitude cycles. This result suggests that the proposed discrete modelling approach can be used to conduct numerical experiments for insights into the fatigue behaviour of cemented materials.

本文提出了一种结合离散元法 (DEM) 和新型粘结接触模型的建模方法，用于表征胶结材料的疲劳响应。虽然 DEM 通常用于模拟发生开裂的粘合材料，但本方法的核心是开发新型粘合疲劳模型。这个新模型结合了损伤力学和界面塑性理论，以捕捉骨料之间水泥桥的疲劳裂纹扩展。由于结合了边界表面塑性，所提出的模型以统一的方式提供了从静态损伤到疲劳损伤的平滑过渡，反之亦然，使其更灵活地捕捉胶结材料在不同载荷条件下的损伤响应（即单调和循环加载）。而且，所提出的方法自动捕获疲劳载荷下骨料之间水泥桥的滞后响应，无需特别处理。更重要的是，通过消除疲劳损伤变量对加载循环次数的直接依赖，该建模方法可用于模拟循环变载荷幅值下胶结材料的疲劳行为。所提出的建模方法根据几个强度测试进行评估，以检查其预测能力。在恒定和可变振幅循环下，弯曲模量退化、寿命和应力水平的敏感性与疲劳实验取得了令人满意的一致。