不同类型煤颗粒侧限压缩变形破碎特性试验研究

Experimental study on confined compression deformation and breakage characteristics for different types of coal particles

煤与瓦斯突出等动力灾害严重制约了矿井的安全生产,而不同类型煤颗粒的加载破碎特征反映了煤体结构、力学特性以及能量存储行为,对煤与瓦斯突出灾害研究具有重要的意义,但目前缺少煤颗粒的破碎特性研究。因此,选取了原煤和构造煤颗粒,开展了不同粒径级配和应力条件下的侧限加载实验研究。结果表明,加载过程依次分为滑移阶段、破碎阶段和压固阶段。在滑移阶段和破碎阶段构造煤抗变形能力均弱于原生煤,但是在压固阶段其应变硬化趋势明显强于原生煤。应力虽然会较大程度影响煤颗粒的相对破碎率,但是在压固阶段该影响较弱。加载过程中由于中粒径中部分煤颗粒结构不稳定,加载过后的煤颗粒存在明显粒径丢失现象。同时粒径级配也影响着煤颗粒的破碎,单一级配试样组中大粒径的试样相对破碎率更高,混合级配试样组的相对破碎率整体比单一级配的要低。相比于原生煤,构造煤的大、中粒径煤颗粒绝对破碎率更高,且破碎过程中更倾向于破碎成粒径更小的煤颗粒,构造煤颗粒破碎程度总高于原生煤。总体而言实验中构造煤颗粒应变硬化现象明显、破碎程度较高,甚至呈现流变特征,这是导致构造煤孔隙率小,渗透率更低的根本原因。且外界对构造煤颗粒输入的能量大都耗散在煤颗粒的摩擦、破碎以及塑性变形,因而储存在其本身的弹性能较低。

Dynamic disasters such as coal and gas outburst seriously restrict the safety of mine production.Different types of coal particles reflect the coal structure,mechanical characteristics and energy storage behavior under load,which is of great significance to the study of coal and gas outburst disasters.However,there is little research on the coal particles breakage characteristics at present.In this study,raw coal and tectonic coal particles were selected to carry out confined compression experiments under different particle size distributions and stress conditions.The results show that the loading process is divided into slip stage,breakage stage and consolidation stage in turn.The deformation resistance of tectonic coal is weaker than that of raw coal in slip stage and breakage stage,but its strain hardening tendency is obviously stronger in compression stage than that of raw coal.Although the stress has a great influence on the relative breakage rate of coal particles,it has a weak influence at the consolidation stage.Due to the unstable structure of some coal particles in the middle particle size during loading,obvious particle size loss occurs after loading.At the same time,particle size distribution also affects the coal particle breakage.The relative breakage rate of large-size sample in single-graded sample group is higher and that of mixed-graded sample group is lower than that of single-graded sample group as a whole.Compared with the raw coal,the absolute breakage rate of large and medium size coal particles of tectonic coal is higher,and tends to break into smaller size coal particles during breakage process.The breakage de-gree of tectonic coal particles is always higher than that of raw coal.In general,strain hardening of tectonic coal particles is obvious,breakage degree is high,and even presents rheological characteristics in the experiment,which is the basic reason for low porosity and low permeability of tectonic coal.Moreover,most of the energy input to tectonic coal particles from outside is dissipated by friction,breakage and plastic deformation of coal particles,so the elastic energy stored in them is low.