摘要
岩层运动和开采扰动加快了深部煤层的裂隙发育和剥落,易导致动力灾害,其中煤层饱水前后动力学性质有所差异,整体失稳破坏程度也有所不同。为探究不同冲击气压下自然状态煤样和饱水煤样的动力学破坏特征,以唐家会煤矿61304工作面裂隙水和老空水对煤体强度的影响为背景,原煤样和饱和水煤样为研究对象,进行霍普金森压杆(SHPB)试验,探究动载冲击下煤样压–拉渐进破坏过程中位移、应变、能量耗散和破碎程度4种指标的变化过程。试验结果表明:(1)煤样裂纹呈现出“发育–贯通–破坏”的渐进变化,大致可分为起裂、裂纹发育、裂纹贯通和最终破坏4个阶段;受水的软化作用,煤样饱水后裂纹发育长度减缓,但裂纹交错的密度和破碎程度较高,且动态抗压强度相较于原煤样数值偏低。(2)煤样的能量演化大致可分为压缩吸能、吸能耗散和能量耗散3个阶段,不同冲击气压(0.3,0.5和0.7 MPa),原煤样的耗散能从24.13 J增加至39.71 J,增加约15.58 J,而饱水煤样的耗散能从7.31 J增加至31.61 J,增加约24.3 J,但原煤样的透射能波动相对平稳(5.06~6.31 J),而饱水煤样透射能的增加程度较大,从0.3 MPa的1.32 J增加至0.7 MPa的9.39 J。(3)煤样的破碎程度随气压的增加而增大,宏观上呈现出颗粒和粉末的破碎特征,煤样饱水后其破碎程度进一步升高;气压较小时(0.3和0.5 MPa),煤样是否饱水其分形维数差别很小,当气压升高至0.7 MPa,饱水煤样的分形维数要高于原煤样14.66%,其破碎后的颗粒度相较于原煤样波动更大。(4)不同冲击气压下煤样压–拉渐进破坏特征试验研究是煤体裂纹扩展传播计算的试验基础,试验总结并归纳了煤样饱水前后4种指标变化特征的差异性,为唐家会煤矿61304工作面顶板旋转下沉和砂岩裂隙水共同作用下煤体的碎裂特征提供一定的参考。
The displacement of layers and mining activities expedite the formation of fractures and spalling in deep coal seams,potentially resulting in dynamic disasters.The dynamic characteristics of coal seams exhibit discrepancies before and after saturation with water,leading to diverse levels of overall instability and failure.To examine the dynamic failure properties of coal samples in natural and saturation states under impact loading conditions,particularly emphasizing the impact of fissure water and goaf water on coal strength at the 61304 working face of Tangjiahu coal mine,split Hopkinson pressure bar(SHPB) tests were carried out on both unaltered coal samples and water-saturated coal samples.The objective of the study was to investigate the variations in displacement,strain,energy dissipation,and degree of fragmentation that occur during the progressive failure of coal samples under dynamic impact loading conditions.The experimental results suggest that:(1) The cracks observed in the coal samples undergo a progressive evolution characterized by four distinct stages:initiation,development,penetration and ultimate failure.The presence of water has a softening effect,causing a deceleration in the length of crack propagation in water-saturated coal samples.However,it leads to an increase in the density of interlaced cracks and the degree of fragmentation.Furthermore,the dynamic compressive strength of coal samples saturated with water is relatively lower in comparison to that of the original coal samples.(2) The energy transformation process of coal samples can be broadly categorized into three stages:compression absorption,absorption dissipation,and energy dissipation.At various impact pressures(0.3,0.5,and 0.7 MPa),the dissipated energy of the untreated coal specimens rose from 24.13 J to 39.71 J,marking an increment of about 15.58J.In contrast,the dissipated energy of the coal specimens saturated with water escalated from 7.31 J to 31.61 J,showing an increase of approximately 24.3 J.The fluctuation of transmitted energy in the original coal samples remains relatively stable(5.06–6.31 J).In contrast,there is a more significant increase in transmitted energy in watersaturated coal samples,ranging from 1.32 J at 0.30 MPa to 9.39 J at 0.70 MPa.(3) The level of fragmentation observed in coal samples escalates as the pressure rises,manifesting macroscopic features akin to particle and powder fragmentation.The level of fragmentation of coal samples escalates following saturation with water.At lower pressures of 0.3 and 0.5 MPa,minimal disparity exists in the fractal dimensions of coal specimens,irrespective of their water saturation levels.When the pressure is elevated to 0.7 MPa,the fractal dimension of water-saturated coal samples increases by 14.66% compared to that of the original coal samples.Additionally,the particle size exhibits more pronounced fluctuations after fragmentation in comparison to the original coal samples.(4) The experimental investigation into the progressive failure characteristics of coal samples under varying loading rates offers an empirical foundation for estimating the propagation of coal crack extension.The experimental results provide a summary and generalization of the variances in the characteristics of the four indicators pre-and postsaturation with water.These findings offer insights into the fracturing characteristics of coal when subjected to the combined effects of roof rotation and sandstone fissure water at the 61304 working face of Tangjiahu coal mine.
作者
党嘉鑫
涂敏
张向阳
赵庆冲
DANG Jiaxin;TU Min;ZHANG Xiangyang;ZHAO Qingchong(Ministry of Education Key Laboratory of Safe and Efficient Mining in Coal Mine,Anhui University of Science and Technology,Huainan,Anhui 232001,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2024年第10期2520-2539,共20页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(52074008)
安徽高校协同创新资助项目(GXXT-2020-056)。
关键词
采矿工程
霍普金森杆
动力学特征
能量耗散
数字图像相关法
分形维数
mining engineering
split Hopkinson pressure bar
dynamic characteristics
energy dissipation
digital image correlation method
fractal dimension
