Abstract The compound dynamic disaster is an abrupt and violent energy-releasing process under the combined action of gas and geological tectonic stress in deep underground coal mines. To investigate the occurrence mechanism of compound dynamic disasters, a novel experimental approach was designed and the one free-face true triaxial tests with different loading rates were conducted. Results shown that the compound dynamic disaster can be classified into several stages: initial quiet period, local particles and fragments ejecting, mid-term quiet period, external coal plate bending accompanied by gas-emitting, dynamic disaster occurring process, and the final re-stabilized period. The presence of the gas can significantly facilitate the development of cracks and enhance the kinetic energy, thus increasing the probability of the compound dynamic disasters. Under the one free-face true triaxial engineering stress conditions, the mechanical properties (e.g. deformation and strength) of coal samples are obviously rate-dependent, and the peak stress exhibits an approximate logarithmically increase trend with increasing loading rate. After failure, several tensile-shear fractures approximately parallel to the intermediate principal stress direction and perpendicular to the free face are generated. And an arc-shaped coal-burst pit on the free face of coal sample is observed, and the pit volume increases with the increase of the loading rate. Moreover, the particle ejection kinetic energy increases gradually as the loading rate increased, suggesting a higher loading rate can enhance the intensity of the disaster. The findings may provide guidance for the prevention and control of the compound dynamic disasters in deep underground coal mines.

中文翻译：

---

加载速率对真三轴应力下深部煤矿复合动力灾害的影响

摘要 复合动力灾害是深部煤矿在瓦斯和地质构造应力共同作用下发生的突然、剧烈的能量释放过程。为研究复合动力灾害的发生机制，设计了一种新的实验方法，并进行了不同加载速率的单自由面真三轴试验。结果表明，复合动力灾害可分为初始静寂期、局部粒子和碎片喷出、中期静寂期、外部煤板弯曲伴随瓦斯喷发、动力灾害发生过程、最后再稳定期。气体的存在可以显着促进裂纹的发展并增强动能，从而增加了复合动力灾害的发生概率。在单自由面真三轴工程应力条件下，煤样的力学性能（如变形和强度）具有明显的速率依赖性，峰值应力随着加载速率的增加呈近似对数增加趋势。失效后，会产生几条近似平行于中间主应力方向并垂直于自由面的拉剪断裂。并在煤样的自由面上观察到一个弧形煤爆坑，坑体积随着装填率的增加而增大。此外，随着加载速率的增加，粒子喷射动能逐渐增加，表明较高的加载速率可以增强灾害的强度。