冲击荷载下类煤岩组合体能量耗散与破碎特性分析
Energy dissipation and crushing characteristics of coal-rock-like combined body under impact loading
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摘要: 利用分离式霍普金森压杆(SHPB)对类煤、岩单体及组合体试件进行冲击压缩试验,分析了试件能量耗散与破碎块度特征,通过对组合体煤、岩两组分碎块分别筛分,得到了各自的平均破碎块度,并依据单体试件平均破碎块度及破碎耗能密度与入射能之间的关系,获得了两种组分的破碎耗能密度,探究了两者吸能特性。结果表明:结合面的存在使得应力脉冲在组合体试件与压杆间传播做功过程更复杂,试件耗散能变化与煤单体接近,而小于波阻抗较大的岩单体。煤组分由于受到岩组分变形抑制作用而能量集聚程度更高,破碎耗能密度与破碎程度大于同等冲击强度下的煤单体,破碎过程岩组分的能量转移亦加剧了煤组分的破碎程度;相反,岩组分破碎耗能密度与破碎程度相比岩单体则偏小。复合煤岩体能量集聚程度更高,发生动力灾害所需的能量更低,在对复合煤岩巷道冲击地压和瓦斯突出动力灾害机理认识上及采取防治措施时应注意此特性。Abstract: The impact compression tests on a single coal-like body, a rock-like body and a combined coal-rock-like body are carried out by using the split Hopkinson pressure bar (SHPB). The energy dissipation and fragmentation characteristics of the specimens are analyzed. By screening the coal and rock fragments respectively, the average fragment sizes are obtained. The energy dissipation densities of the two sections are obtained according to the relationship among average fragment size, energy dissipation density and incident energy of single bodies, and the energy absorption characteristics of the two sections are investigated. The results show that the existence of the joint surface makes the propagation of stress pulse between combined specimens and elastic bars more complex, and the dissipated energy is close to that of the single coal body, however smaller than that of the single rock body with large impedance. The degree of energy accumulation of coal section is higher because of the deformation inhibition of the rock section, and the energy dissipation density and crushing degree of coal section are greater than those of the single coal body under the same impact intensity, and the energy transfer of rock section aggravates the crushing degree of the coal section. On the contrary, the energy dissipation density and the crushing degree of rock section are smaller than those of the single rock body. The energy needed for dynamic disaster of composite coal and rock is lower than that of the single coal body because of the higher energy accumulation degree. These conclusions should be considered when understanding the mechanism of rock burst and coal and gas outburst and taking prevention and control measures for these dynamic disasters.