In order to study the nonlinear creep mechanism of concrete materials, predict and evaluate the safety of the structure, uniaxial nonlinear creep tests of concrete specimens under different ages and stress-strength ratios ($\sigma /f_c$) were carried out. Based on the discrete element theory (DEM), a concrete three-phase numerical simulation model is established, which considers the real aggregate shape and the strength difference of each phase material. The study found that the nonlinear creep duration of the early-age concrete specimens increases exponentially with age, and decreases exponentially with the increase of stress-strength ratio. Age has the greatest influence on total deformation of concrete nonlinear creep. The quantitative relationship between creep characteristics (duration, total deformation) and control variables (age, stress-strength ratio) is established. The numerical simulation model simulates the uniaxial nonlinear creep process of the concrete specimen. Compared with the measured data, it is found that the creep curve is in good agreement. At the same time, the overall trend of the measured damage value defined by the wave velocity and the damage simulation value defined by the number of cracks is in good agreement, which objectively reflects the general law of damage and crack development in the nonlinear creep process. Through the analysis of the failure mode and fabric diagram of the concrete specimen, the microcracks first occurred on the interface. At the same time, the cement gel in the cement mortar undergoes viscous flow, the stress is redistributed, and the microcracks continue to produce, expand, and connect, which ultimately leads to the complete failure of the specimen. The quantitative relationship and numerical simulation model proposed in this paper can be applied to the creep prediction and safety calculation of components or buildings under the condition of high stress-strength ratio, and has a good engineering application prospect.

为了研究混凝土材料的非线性蠕变机理，预测并评估结构的安全性，对不同年龄和应力-强度比的混凝土试件进行单轴非线性蠕变试验（$\sigma /F_C$）进行。基于离散元理论（DEM），建立了一个具体的三相数值模拟模型，该模型考虑了实际骨料的形状和每种相材料的强度差。研究发现，早期混凝土试件的非线性蠕变持续时间随着年龄的增长呈指数增长，而随着应力强度比的增加呈指数下降。年龄对混凝土非线性蠕变的总变形影响最大。建立蠕变特性（持续时间，总变形）与控制变量（年龄，应力-强度比）之间的定量关系。数值模拟模型模拟了混凝土试样的单轴非线性蠕变过程。与实测数据比较，发现蠕变曲线吻合良好。同时，由波速定义的实测损伤值与由裂纹数定义的损伤模拟值的总体趋势吻合良好，客观地反映了非线性蠕变过程中损伤和裂纹发展的一般规律。 。通过对混凝土试样破坏模式和结构图的分析，微裂纹首先出现在界面上。同时，水泥砂浆中的水泥凝胶经历粘性流动，应力被重新分配，并且微裂纹继续产生，膨胀和连接，最终导致试样完全破坏。