煤岩组合体破坏前能量积聚规律试验研究
Experimental study on the law of energy accumulation before failure of coal-rock combined body
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摘要: 煤系地层是由多种岩层相间互层构成的,每种岩层的力学性质不同,其能量积聚能力也不同,这就导致了煤岩系统中的能量分布具有不均等性,为探索煤岩系统中的能量积聚规律,确定引发冲击地压的能量积聚关键层位,对自主构建的不同岩性和煤岩比例的组合体开展单轴压缩试验。结果表明:①随着煤岩比例的增大,组合体破坏区域由整体破坏到半整体破坏到局部破坏逐渐过渡,破坏类型由“碎状”完全破坏、“Y型”半完全破坏到“点式”不完全破坏逐渐过渡。②随着煤岩高度比增加,组合体强度、弹性模量逐渐减小、峰前能量逐渐增多;岩石组分对于组合体的强度和弹性模量具有一定的提升作用,岩石组分的硬度越大,组合体的强度和弹性模量也越大,但组合体峰前能量越少。煤岩组合体的冲击能量指数均在5.164~6.049,具有强冲击倾向。③构建了煤岩组合体力学模型,基于煤岩结构特征及其力学特性分析借助组合体和组分的应力-应变曲线,推导了同径煤岩组合体与非同径煤岩组合体破坏前的能量分布计算公式。④细砂岩-煤组合体中煤组分积聚能量占比在60.00%~94.54%,细砂岩组分积聚能量占比在5.46%~40.00%;粗砂岩-煤组合体中煤组分积聚能量占比在54.55%~89.64%,粗砂岩组分积聚能量占比在10.36%~45.45%;三元组合体煤组分能量积聚占比为66.13%,78.48%,粗砂岩组分积聚能量占比为19.35%,13.29%,细砂岩组分积聚能量占比为14.52%,8.23%。所有组合体中煤组分积聚能量占比均大于50%,煤组分是能量积聚的主要载体。组合体各组分的能量积聚顺序为:煤>粗砂岩>细砂岩,弹性模量小的软弱岩层(煤层),能量积聚能力更强。随着煤岩比例增大,煤组分能量占比也增大。⑤理论分析了煤岩组合体能量积聚规律,揭示了深部开采活动中冲击地压的易发机制,并且针对坚硬顶板-煤体-坚硬底板这种能量承载结构,从能量积聚层位的角度,提出了直接释能和间接释能2种能量缓控理念及措施,并进行工程实践。微震监测和巷道变形观测结果表明:直接释能和间接释能措施破坏了能量承载结构,有效释放了其中的能量,防止了冲击地压的发生。Abstract: The coal measures strata are composed of many kinds of rock strata, and the mechanical properties of each rock strata are different, and their energy accumulation capacities are also different, which leads to the uneven energy distribution in the coal-rock system.In order to explore the law of energy accumulation in the coal-rock system and determine the key layers of energy accumulation leading to rock burst, uniaxial compression tests were carried out on combined bodies with different lithology and coal-rock ratio.The results show that:① with the increase of the ratio of coal-rock, the failure area of the combined bodies gradually changes from overall failure to semi-global failure to local failure, and the failure type gradually changes from “fragmentation” complete failure, “Y type” semi-complete failure to “point type” incomplete failure.② With the increase of coal-rock height ratio, the strength and elastic modulus of the combined bodies gradually decrease, and the pre-peak energy increases gradually, and the rock component can improve the strength and elastic modulus of the combined bodies to a certain extent, and the greater the hardness of the rock component, the greater the strength and elastic modulus of the combined bodies, but the less the pre-peak energy of the combined bodies.The impact energy index of coal-rock combined bodies is between 5.164 and 6.049,which has a strong impact tendency.③ The mechanical model of coal-rock combined body was constructed, and based on the analysis of coal-rock structure and mechanical properties, with the help of the stress-strain curves of combined bodies and components, the formula for calculating the energy distribution of the same diameter coal-rock combined body and non-same diameter coal-rock combined body before failure was derived.④ The proportion of accumulated energy of coal components in fine sandstone-coal combined bodies is between 60.009% and 94.54%,and that of fine sandstone is between 5.46% and 40.005%.The proportion of accumulated energy of coal components in coarse sandstone-coal combined bodies is between 54.55% and 89.64%,and that of coarse sandstone is between 10.36% and 45.45%.The energy accumulation ratio of coal components of ternary combined bodies is 66.13% and 78.48%,that of coarse sandstone components is 19.35% and 13.29%,and that of fine sandstone components is 14.52% and 8.23%.The proportion of accumulated energy of coal components in all combined bodies is more than 50%,and coal components are the main carriers of energy accumulation.The order of energy accumulation of each component of the combined body is coal > coarse sandstone > fine sandstone, and the weak rock(coal seam) with low elastic modulus has stronger energy accumulation ability.With the increase of the ratio of coal-rock, the energy proportion of coal components also increases.⑤ The law of energy accumulation of coal-rock combined bodies was analyzed theoretically, and the prone mechanism of rock burst in deep mining was revealed.Aiming at the energy bearing structure of hard roof-coal-hard floor, from the point of view of energy accumulation layer, two energy slow control concepts and measures of direct release of energy and indirect release of energy were put forward, and the engineering practice was carried out.The results of micro-seismic monitoring and roadway deformation observation show that the direct and indirect energy release measures destroy the energy bearing structure, release the energy effectively and prevent the occurrence of rock burst.