不同加载速率下煤岩动力破坏特征实验研究

Experimental study on dynamic failure characteristics of coal and rock under different loading

临空侧巷道作为煤岩动力灾害的主显现体,探明回采过程中临空侧巷道煤岩动力显现及破坏特征,是采场安全高效生产的前提。基于此,采用高频振动采集及孔内成像三轴动静载试验系统,开展了不同加载速率下煤岩真三轴单面临空实验,揭示了加载速率对煤岩动力破坏的影响机制。研究结果表明:1)不同加载速率下煤岩系统损伤破坏从临空面逐渐向深部转移:加载速率较小时,煤岩系统做出充分适应性调整,破坏特征及声发射信号具有明显的前兆规律,系统承载失稳发生前,临空侧煤岩张拉扩容、深部煤粉(颗粒)外流,声发射信号持续处于“高频高能”状态,加载速率的增大,裂隙发育受到抑制,原生裂隙尖端应力的骤增,临空侧煤岩层裂抛射,局部颗粒弹射动能大,声发射信号呈现“高频低能”状态,无前兆信息;2)临空面煤岩均以张拉破坏为主,加载速率的增大,深部煤岩破坏形式呈现由屈曲层裂张拉破坏-剪切、张拉复合破坏-剪切破坏的转变;3)加载速率较小时,煤岩系统裂隙较为发育,强度弱化,能量充分释放,加载速率增大,煤岩系统失稳峰值强度、破碎程度、抛射质量和动能都有较大增加,动力显现更为迅猛,加载速率的增加对煤岩动力破坏起到了正向激励作用。

Airside roadway is known for being the primary location where coal or rock dynamical disas-ters occur.Verifing the dynamic manifestation and damage characteristics of the coal-rock system in air-side roadway during mining operations is crucial for ensuring safe and efficient production in mining are-as.Using a high-frequency vibration acquisition and in-hole imaging three-axis dynamic-static load test system,the true triaxial single-side hanging experiments were performed on coal-rock samples under dif-ferent loading rates to reveal the influence mechanism of loading rate on coal-rock dynamic failure.The research findings are summarized as follows:1)Under different loading rates,the damage and failure of the coal-rock system progressively shift from the hanging face to deeper regions.At lower loading rates,the coal-rock system undergoes adaptive adjustments,and its failure characteristics and acoustic emission signals exhibit clear precursor patterns.Prior to reaching bearing instability,the coal-rock on the hanging side experiences tension expansion,leading to the outflow of coal dust particles from deeper regions.Acoustic emission signals persist in a state of"high frequency,high energy."However,as the loading rate increases,crack development is suppressed,resulting in a sudden increase in stress at the tip of primary cracks.Consequently,the hanging coal-rock layer fractures and ejects,generating a significant amount of kinetic energy from local particle ejection.The acoustic emission signals transition into a state of"high frequency,low energy"without exhibiting any precursor information.2)Tensile failure predominates on the hanging face of the coal-rock.With an increase in the loading rate,the failure pattern in the deeper coal-rock transitions from flexural tensile failure to a combination of tensile-shear failure and shear failure.3)At lower loading rates,the coal-rock system exhibits well-developed cracks,weakened strength,and substantial energy release.However,as the loading rate increases,the peak strength,degree of fragmentation,ejection mass,and kinetic energy of the coal-rock system all experience significant growth,resulting in a more rapid dynamic manifestation.The increase in loading rate serves as a positive stimulus for the dynamic failure of coal-rock.