压缩状态下煤体波速特性及损伤破坏演化规律研究

Wave velocity characteristics and damage evolution law of coal under compression

为采用超声波波速评价煤体破坏状态,针对淮南矿区煤体,运用岩石力学试验机和波速监测设备,开展了单轴压缩状态下煤体声波及变形实时监测室内试验,获得了波速及煤体表面破坏形态演化特征,引入以波速定义的损伤变量量化煤体破坏过程,探讨煤体破坏前兆声学信息。研究结果表明:随煤体轴向应变的增加,波速呈现平稳、缓慢降低再急剧降低的变化趋势,煤样表面形态先后经历无明显变化、出现小范围的宏观破坏直至完全破坏的变化特征;随煤岩变形的增大,损伤变量具有平稳在0附件、缓慢增长再急剧增大的基本规律;煤体持续受载过程中,当应变水平值达到95.55%,应力水平值达到95.68%时,波速水平值为96.32%时,煤体裂纹快速扩展,即将发生失稳灾害。研究结果可为预测防控煤岩失稳灾害提供试验依据。

In order to evaluate the failure state of coal body based on ultrasonic wave velocity,the coal samples from Huainan mining area are tested in the lab,the sound wave and deformation of coal is monitored in real-time under uniaxial compression using rock mechanics testing machine and wave velocity monitoring equipment.The evolution characteristics of wave velocity and coal surface failure morphology is obtained,the damage variable defined by wave velocity is introduced to quantify the coal failure process,and the acoustic information of coal failure precursors is discussed.The results show that:Firstly,with the increase of axial strain of coal body,the wave velocity changed in the sequence of stable,reducing slowly and then reducing sharply;the surface morphology of coal samples showed no obvious change at the beginning,then small-scale macro failure appeared and developed to complete failure.Secondly,with the increase of coal and rock deformation,the damage variable was steady at 0,then grew slowly and rise sharply later.Thirdly,during continuous loading of coal,when the strain level reaches 95.55%,the stress level reaches 95.68% and the wave velocity level is 96.32%,the coal crack expands rapidly and the instability disaster is about to occur.The research results can provide experimental basis for predicting and preventing coal and rock instability disasters.