In underground tunnels, caverns or pillar goaf, the time-dependent deformation or failure of the rock or coal mass is a major safety concern, which affects the mechanical properties and stability of the coal and rock in the underground excavations. However, the damage surrounding rock or coal usually occurs from the time mining starts. This initial damage is rarely considered during the current creep tests used for coal. In the present study, an experimental specimen processing method to identify the initial damage to a coal deposit is suggested. The effect of the strain history on the deformation of coal samples with initial damage during multi-level loading triaxial compression creep tests was studied. The laboratory tests showed that the strain versus creep curve of the coal samples experiences three typical creep stages of deceleration creep in the early stage, constant velocity creep in the medium term and catastrophic accelerated creep in the later stage. With the increase in initial damage, it was observed the gradual decrease in total creep time, deviating stress of creep failure, stress threshold of accelerated creep and starting time of the volume expansion. When the initial damage value increased from 0.0 to 0.50, the deviating stress of creep failure, stress threshold of accelerated creep and starting time of the volume expansion of the coal decreased by 42.3%, 48.5% and 51.4%, respectively. The study is of great significance to conduct researches on the deformation, mechanical characteristics and long-term strength of coal pillar with initial damages under long-term pressure, and also provides insight into the underground excavations and the design of supports to the opneings under such disturbance.

在地下隧道，洞室或竖井采空区中，岩石或煤块随时间变化的变形或破坏是一个主要的安全隐患，这会影响地下开挖中煤和岩石的力学性能和稳定性。但是，围岩或煤的破坏通常从开采开始就发生。在当前用于煤炭的蠕变测试中，很少考虑这种初始损坏。在本研究中，提出了一种确定标本对煤层的初始破坏的实验性标本处理方法。研究了应变历史对多级载荷三轴压缩蠕变试验中初始损伤的煤样品变形的影响。实验室测试表明，煤样的应变-蠕变曲线经历了早期的三个典型蠕变阶段：减速蠕变，中期等速蠕变和后期的灾难性加速蠕变。随着初始损伤的增加，观察到总蠕变时间逐渐减少，蠕变破坏的应力偏离，加速蠕变的应力阈值和体积膨胀的开始时间。当初始损伤值从0.0增加到0.50时，蠕变破坏的偏应力，加速蠕变的应力阈值和煤的体积膨胀开始时间分别降低了42.3％，48.5％和51.4％。该研究对开展变形研究具有重要意义，