岩石的蠕变特性是影响岩体工程稳定性的重要因素，而岩石的长期强度是确定岩体工程长期稳定的一个重要指标。由于岩石材料的非均质性，其长期强度具有明显的尺寸效应。为了研究岩石长期强度的尺寸效应，首先，在幂函数模型基础上，基于损伤力学理论，建立了能够描述岩石蠕变全过程的非线性蠕变损伤模型；然后，把运用该模型计算得到的单轴压缩蠕变数值模拟结果与室内单轴压缩蠕变试验结果进行对比，验证了模型的正确性；最后，采用所提出的模型对7个不同尺寸的岩样进行了单轴压缩蠕变数值模拟，并对岩石长期强度尺寸效应进行了分析。数值模拟结果表明：随着试样尺寸的逐渐增大，岩石长期强度值逐渐减小，当试样尺寸增大到一定程度时，岩石长期强度稳定在一个特定值附近。

Rock creep is an important factor affecting the stability of rock engineering. The long-term strength of rock, which shows an obvious size effect due to rock heterogeneity, is an important mechanical index for evaluating the long-term stability of rock engineering. The aim of this study is to investigate the size effect of long-term strength of rock. Firstly, on the basis of classical power law creep model and damage mechanics principle, a nonlinear creep damage model is established for describing the whole process of rock creep. Then, by comparing the numerical results of uniaxial compression creep test based on the proposed model with the results of indoor uniaxial compression creep test, the applicability of the model is verified. At last, numerical simulation tests are performed on seven rock specimens with different sizes under uniaxial compression creep. The size effect for long-term strength of rock is analyzed. The numerical simulations indicate that, the long-term strength of rock decreases with the increasing of size; but it will be constant when the size of the rock exceeded a specific size.