In the underground tunnels, caverns or bord-and-pillar goaf, the initial damage usually occurs in the surrounding rock or in coal when mining starts. Under the frequent influence of mining stress, mechanical properties of the surrounding coal rock with initial damage, especially the long-term creep performance, are related to the safety and stability of underground engineering. However, under different loading rate, this initial damage is rarely considered during the current testing methods used for coal. In the present study, a method of preparing coal samples with initial damage by cyclic pre-loading and unloading is innovatively proposed. The mechanical and creep properties of the initially damaged coal specimen under loading rates of \(0.002~\text{mm}\cdot \text{s}^{-1}\), \(0.005~\text{mm}\cdot \text{s}^{-1}\), \(0.01~\text{mm}\cdot \text{s}^{-1}\), \(0.05~\text{mm}\cdot \text{s}^{-1}\) and \(0.1~\text{mm}\cdot \text{s}^{-1}\) are investigated. The laboratory tests results showed that after the loading rate increased to \(0.05~\text{mm}\cdot \text{s}^{-1}\), the compression stage of micro-cracks gradually became longer, and the elastic deformation stage began to shorten. The existence of initial damage has promoted the development and expansion of some cracks in the coal sample such that with the increase in loading rate, the deviatoric stress of initial damage samples (IDS) was flat first and then underwent a gradual increase. In the creep test, with the increase of the loading rate, the instantaneous strain of IDS showed a nonlinear change, first decreasing and then increasing, with \(V = 0.01~\text{mm}\cdot \text{s}^{-1}\) as the inflection point. As the loading rate increased, the stress threshold gradually declined and then increased, and the deviatoric stress of the IDS creep damage gradually increased nonlinearly. This study can provide insight into the underground excavations and the design of supports to the openings under such a disturbance.

在地下隧道，洞穴或采空区和采空区采空区中，开采开始时，最初的破坏通常发生在周围的岩石或煤炭中。在采矿应力的频繁影响下，具有初始破坏作用的煤岩的力学性能，特别是长期蠕变性能，与地下工程的安全性和稳定性有关。然而，在不同的加载速率下，在当前用于煤的测试方法中很少考虑这种初始损坏。在本研究中，创新性地提出了一种通过循环预装和卸料来制备具有初始损伤的煤样品的方法。在\（0.002〜\ text {mm} \ cdot \ text {s} ^ {-1} \）的加载速率下，初始损坏的煤样品的力学和蠕变特性，\（0.005〜\ text {mm} \ cdot \ text {s} ^ {-1} \），\（0.01〜\ text {mm} \ cdot \ text {s} ^ {-1} \），\（研究了0.05〜\ text {mm} \ cdot \ text {s} ^ {-1} \）和\（0.1〜\ text {mm} \ cdot \ text {s} ^ {-1} \）。实验室测试结果表明，加载速率增加到\（0.05〜\ text {mm} \ cdot \ text {s} ^ {-1} \），微裂纹的压缩阶段逐渐变长，弹性变形阶段开始缩短。初始损伤的存在促进了煤样品中某些裂纹的发展和扩展，以致于随着装填速率的增加，初始损伤样品（IDS）的偏应力首先变得平坦，然后逐渐增加。在蠕变试验中，随着加载速率的增加，IDS的瞬时应变呈现非线性变化，先减小后增加，\（V = 0.01〜\ text {mm} \ cdot \ text {s} ^ { -1} \）作为拐点。随着加载速率的增加，应力阈值逐渐降低，然后升高，IDS蠕变损伤的偏应力逐渐非线性增加。这项研究可以提供对地下开挖的深入了解，以及在这种扰动下对洞口的支撑设计。