静动组合三轴加载煤岩强度劣化试验研究

Experimental research on coal and rock strength deterioration under combined static and dynamic triaxial loading

基于煤岩力学伺服三轴压缩试验系统,辅以声发射检测,对彬长矿区某矿煤岩进行高应力下不同频率动载试验,研究煤岩动载诱发后破坏机理与强度劣化规律。结果表明:煤岩动载扰动后强度劣化明显,峰值强度、应变与动载频率呈负相关;动载扰动后煤岩内部裂隙进一步发育,提前进入屈服变形;煤岩破坏首先从内部开始,逐渐延伸至表面,破坏形式由剪切破坏变为横向拉伸破坏。声发射定位点由中心向外部扩展,大量分布在煤岩表面,与煤岩裂隙发育区域及主要破坏方向基本保持一致;声发射能量事件主要发生在动载加载初期阶段及峰值阶段且峰值阶段达到最大,能量与煤岩应力水平呈正相关,破坏后能量迅速回落。煤岩动载结束后继续静载加载到其动载最大应力阶段前无声发射能量事件产生,发生明显凯泽现象;临近峰值破坏阶段声发射能量迅速回落,此特性可作为预测煤岩破坏的前兆。

Based on the servo-triaxial compression test system of coal and rock mechanics,supplemented by acoustic emission detection,a dynamic load test of coal and rock under high stress at different frequencies in Binchang mining area was carried out to study the failure mechanism and strength degradation law of coal and rock induced by dynamic load.The results show that the strength of coal and rock is obviously degraded after dynamic load disturbance.The peak strength and strain are negatively correlated with the dynamic load frequency;after the dynamic load disturbance,the internal cracks in the coal and rock further develop and enter the yield deformation ahead of time;the failure of coal and rock first starts from the inside and gradually extend to the surface,the failure mode changes from shear failure to transverse tensile failure.Acoustic emission positioning points extend from the center to the outside and are distributed in large numbers on the surface of coal and rock,which are basically consistent with the development area of coal and rock fissures and the main failure directions;acoustic emission energy events mainly occur in the initial stage and peak stage of dynamic load loading and reach the maximum in the peak stage,the energy value is positively correlated with the stress level of coal and rock,and the energy drops rapidly after failure.After the coal dynamic loading is over,the silent emission energy event occurs before the static load continues to the maximum stress stage of the dynamic load,and the obvious Kaiser phenomenon occurs;the acoustic emission energy drops rapidly near the peak failure stage,this feature can be used as a precursor to predict coal and rock failure.