Jiangsu Vocational Institute of Architectural Technology, Xuzhou 221116, China.
State Key Laboratory of The Gas Disaster Detecting, Preventing and Emergency Controlling, Chongqing 400037, China.
Int J Environ Res Public Health. 2022 Apr 9;19(8):4546. doi: 10.3390/ijerph19084546.
In order to further explore the relationship between the excavation speed and the damage of surrounding rocks and dynamic manifestation, the stress paths of unloading confining pressure and loading axial pressure were designed based on the changes in the roadway surrounding rock stress in this study. Additionally, the mechanical properties and energy evolution law of the coal body were investigated under various unloading rates. As the unloading rate increased, the mechanical properties of the coal body including the failure strength, the confining pressure, the axial strain, and horizontal strain tended to decrease at the rupture stage, while the volume strain and the elastic modulus increased, indicating that the rupture form evolved from the ductile failure to brittle failure. Regarding the energy, the axial pressure did positive work while the confining pressure did negative work, with the total work and the stored elastic strain energy decreasing. In addition, with the increase of the dissipation energy, the elastic strain energy conversion rate decreased linearly, indicating that the high unloading rate increased the possibility of dynamic disasters induced by the instantaneous brittle rupture of the coal body. On the other hand, due to the low releasable elastic strain energy stored in the coal body, the strength and probability of subsequent dynamic manifestation of coal body destruction were reduced. Therefore, increasing the excavation speed in a controllable way can benefit the safety of mining.
为了进一步探讨挖掘速度与围岩损伤和动力表现之间的关系，本研究基于巷道围岩应力的变化，设计了卸围压和加轴压的应力路径。此外，还研究了不同卸荷率下煤体的力学特性和能量演化规律。随着卸荷率的增加，煤体的力学性能，包括破坏强度、围压、轴向应变和水平应变，在破裂阶段趋于降低，而体积应变和弹性模量增加，表明破裂形式从延性破坏演变为脆性破坏。关于能量，轴压做正功，围压做负功，总功和存储的弹性应变能减少。此外，随着耗散能量的增加，弹性应变能转换率线性下降，表明高卸荷率增加了煤体瞬时脆性破裂引发动力灾害的可能性。另一方面，由于煤体中储存的可释放弹性应变能较低，煤体破坏后的强度和后续动力表现的概率降低。因此，以可控的方式增加挖掘速度有利于采矿安全。
