循环加卸载下含瓦斯煤能耗与渗流特性研究

以马兰矿8#煤层煤样为研究对象,进行不同围压下的采动轴向循环加卸载实验,研究煤体渗流特性及能耗损伤特征。结果表明:随着轴向应力的循环加卸载,σ1-ε1曲线呈现螺旋式上升,卸载曲线与下一次的加载曲线之间形成明显的滞回环,加卸载渗透率-应变曲线逐渐变为细长的"条带状"曲线,并在较低围压下出现交叉;随着加卸载次数的增加,渗透率绝对恢复率减小,最大降低率达20%左右,围压越大渗透率恢复越困难。随着加卸载上限应力的增大,煤体在加卸载过程中吸收的总能量、弹性能和耗散能均随着循环次数的增加而增加,煤体的损伤变量也在增大,但增加速率较缓;在循环加卸载结束至煤体屈服点阶段,渗透率随损伤增加呈对数函数减小,直至达到渗透率最低点;在屈服点至煤体破坏阶段,煤体损伤变量增加速率变快,渗透率随损伤的增加呈指数函数增大,煤体开始加速破坏。

Study on energy consumption and seepage characteristics of coal containing gas under cyclic loading and unloading

Abstract: Taking the 8# coal seam coal sample of Malan Mine as the research object, the mining axial cyclic loading and unloading experiment under different confining pressures was carried out to study the seepage characteristics and energy damage characteristics of coal body.The results show that with the cyclic loading and unloading of axial stress, the 1-1 curve presents a spiral rise, and an obvious hysteresis loop is formed between the unloading curve and the next loading curve. The permeability-strain curve gradually turns into an elongated "strip" curve and crosses at a lower confining pressure.With the increase of loading and unloading times, the absolute recovery rate of permeability decreases, and the maximum reduction rate is about 20%. The larger the confining pressure, the more difficult it is to recover the permeability. With the increase of the upper limit stress of loading and unloading, the total energy, elastic energy and dissipated energy absorbed by the coal body in the loading and unloading process all increase with the increase of cycle times, and the damage variable of the coal body also increases, but the rate of increase is slow. At the stage from the end of cyclic loading and unloading to the yield point of coal, the permeability decreases logarithmically with the increase of damage until the lowest point of permeability is reached. At the stage from yield point to coal body failure, the rate of coal body damage variable increases rapidly, the permeability increases exponentially with the increase of damage, and the coal body begins to accelerate the failure.