加卸载速率对含瓦斯煤损伤-渗透时效特性影响试验研究

Experiments study on effects of loading and unloading rates on damage-permeability aging characteristics of gas-bearing coal

为探索轴压加载速率和围压卸载速率对采动含瓦斯煤损伤-渗透时效特性的影响规律,利用煤岩吸附-渗流-力学耦合特性测定仪开展了不同加卸载速率条件下煤体损伤-渗透试验。研究结果表明,轴压加载速率或围压卸载速率越高,试样损伤破坏的时间响应越快,峰值强度呈小幅度降低,即加卸载速率显著影响着试样损伤破坏的时效特性,但对试样抵抗破坏的能力影响较小;加卸载速率较低时试样呈相对稳态损伤,加卸载速率较高时试样损伤程度较高且呈非稳态损伤特征,易发生突崩式破坏;加卸载速率越高,则试样渗透率的时间响应越快,增幅越大,恒轴压卸围压试样的峰后渗透率可达到原始渗透率的163.0%~206.3%;围压卸载对采动煤体损伤-渗透的影响作用远大于轴压加载,因此在工程实践中需适当控制煤层开采速度,以有效避免煤岩瓦斯动力灾害。

For exploring the effects of the loading and unloading rates on the damage-permeability aging characteristics of gas-bearing coal,the damage-permeability experiments for gassy coal were performed with the different loading and unloading rates by the experimental equipment for coupling adsorption-seepage-mechanic properties in the paper.The results show that the higher the axial loading rate or confining pressure unloading rate is,the faster the time response of the coal damage is and the slightly lower the peak strength of coal is; that is,the loading and unloading rates significantly affect the aging characteristics of coal damage,but have less effects on the ability of coal to resist failure.The coal samples are damaged steadily with the lower loading and unloading rates while the coal samples are damaged and destroyed acutely with the higher loading and unloading rates.The higher the loading and unloading rates are,the faster the time response to the permeability is and the larger permeability increase is; the post-strength permeability of the coal with the conditions of decreasing confining pressure and fixing axial loads can reach 163.0% ~ 206.3% of the original permeability.The effect of confining pressure unloading on the damage-permeability characteristics of mining coal mass is much greater than that of axial loading and thus the coal mining speed should be properly controlled for avoiding the coal-rock gas dynamic hazards in the engineering practices.