Bulking characteristics of gangue are of great significance for the stability of goafs in mining overburden in the caving zones. In this paper, a particle discrete element method with clusters to represent gangue was adopted to explore the bulking coefficient time effect of the broken rock in the caving zone under three-dimensional triaxial compression condition. The phenomena of stress corrosion, deformation, and failure of rock blocks were simulated in the numerical model. Meanwhile, a new criterion of rock fragments damage was put forward. It was found that the broken rock has obvious viscoelastic properties. A new equation based on the Burgers creep model was proposed to predict the bulking coefficient of broken rock. A deformation characteristic parameter of the prediction equation was analyzed, which can be set as a fixed value in the mid- and long-term prediction of the bulking coefficient. There are quadratic function relationships between the deformation characteristic parameter value and Talbot gradation index, axial pressure and confining pressure.

煤矸石的松散特性对崩落区开采覆盖层采空区的稳定性具有重要意义。本文采用以簇表示脉石的粒子离散元方法，探讨三维三轴压缩条件下崩落区破碎岩石的膨胀系数时间效应。数值模型模拟了岩块的应力腐蚀、变形和破坏等现象。同时，提出了新的岩屑损伤判据。发现破碎的岩石具有明显的粘弹性能。提出了一种基于Burgers蠕变模型的新方程来预测破碎岩石的膨胀系数。分析了预测方程的变形特征参数，可在膨胀系数的中长期预测中设置为固定值。变形特征参数值与Talbot级配指数、轴压和围压之间存在二次函数关系。