冲击荷载对煤岩内部微结构演化及表面新生裂隙分布规律的影响

Effects of dynamic loads on development of internal microstructure and distribution of new surface fractures of coal

利用自制落锤式煤岩冲击加载试验装置,配合超声波检测设备,对型煤在不同冲击荷载作用下内部微结构及表面新生裂隙的发展演化规律进行系统的试验研究,并分析冲击荷载对型煤内部微结构演化产生影响的机制。结果表明：型煤内部微结构演化与冲击荷载作用次数、单次冲击能量大小、冲击能量施加顺序、冲击能量的累计效果等因素有关;型煤内部微结构的扩展和表面新生裂隙的出现、发展均表现出明显的各向异性,沿冲击荷载方向上比垂直冲击方向上变化显著;相同的冲击荷载作用下,型煤内部微结构总数量随着冲击次数的增加呈现出“高速增加→平缓发展→急速增加”的趋势;不同冲击荷载作用时,随着单次冲击能量的增加,型煤内部微结构总数量呈指数函数关系增大,型煤表面新生裂隙局部化分布特点更为显著;型煤内部微结构演化对冲击能量由大到小进行施加更为敏感;冲击荷载对型煤内部微结构影响的累计效果也呈非线性规律,表现为先增大后减小趋势,其不可简单等效为冲击能量的增加;型煤对冲击能量的吸收率随着单次冲击能量的增加呈减小趋势,表现为大于一定值的较小冲击能量的累计效果要大于等值单次较大冲击能量对型煤造成的影响。

The tests to study the development of internal micro-structure and the distribution of new surface fractures of coal samples under impact loads were performed with the drop hammer impact test equipment for coal and the ultrasonic detection device. The effect of dynamic loads on the development of internal structure of coal was analyzed. The results show that the development of the internal micro-structure of coal is related to the number of impacts,energy of a single impacting,sequence of impact energy,accumulative effect of impact energy,etc. Both the internal micro-structure and the newly developed surface fractures propagate anisotropically. The influence is larger along the impact direction than perpendicular to the direction. When the energy of a single impacting is constant,the total quantity of the internal micro-structure of coal has a trend of rapid increasing,gentle development and sharp increasing with increase of the impact number. The total quantity of internal micro-structure of coal increases exponentially as the energy of a single impacting increases,and the localized distribution of new developed surface fractures of coal is also more significant. The development of the internal micro-structure of coal is more sensitive under the decreasing cyclic loading than in increasing process. The accumulative effect of impact loads on the development of internal micro-structure is nonlinear,and shows a decreasing trend after the first increase. The accumulative effect of impact loads cannot be only simply considered due to the increasing of impact energy. The absorption rate of impact energy of coal decreases as the increase of the impact energy. The accumulative effect of the smaller single impact energy on internal micro-structure of coal is greater than the effect caused by the equivalent larger single impact energy.