深部煤岩超低摩擦效应能量特征试验研究

Experimental research on energy characteristics of anomalously low friction effect in deep coal and rock mass

高地应力和开采强扰动作用下,采场周围的岩体不断发生震动、变形和破坏,形成块系岩体。当深部煤岩积聚能量达到失稳临界值,块系岩体很容易在周围荷载作用下因动力扰动而能量突然释放,发生层间滑动,导致块系岩体发生超低摩擦滑动失稳,从而最终诱发新的冲击地压类型,即超低摩擦型冲击地压灾害,其本质是能量积聚和失稳释放过程。为揭示深部煤岩超低摩擦效应能量特征,以花岗岩和煤两种岩性的块系岩体为研究对象,采用试验研究方法,自主研发了超低摩擦效应试验装置,以轴压和围压模拟高地应力作用,以垂直振动和水平冲击模拟开采强扰动,进行了工作块体分别为完整岩块、破碎岩块和煤块的超低摩擦效应模拟试验。试验结果与已有研究结论进行对比,验证了试验方案的合理性和可行性。以工作块体水平位移的单位质量动能总量作为超低摩擦效应能量变化的特征参数,分析轴压、工作块体数量和岩性对工作块体水平位移单位质量动能时域和频域曲线影响,得到了开采深度、块体破碎程度和岩性与块体动能间关系规律。结果表明:发生超低摩擦效应时,工作块体动能具有集聚效应、短时峰值特性和间歇性。破碎程度和岩性是影响超低摩擦型冲击地压动能总量变化重要因素。试验再现了冲击地压由前震到主震过程,发现超低摩擦型冲击地压能量释放时,块体动能具有由高频向低频转移的频移特性,主频主要处于20 Hz以内的低频区,与冲击地压现场观测结果基本一致。提出以能量释放试验反演冲击地压震级计算方法,以辽宁红阳三矿为例,所得结果与现场监测震级十分接近。

Under a high in-situ stress and strong excavation disturbance,the rock mass around the stope is constantly shocked,deformed and destroyed,forming blocky rock mass.When the accumulation energy of deep coal rock reaches the critical value of instability,the blocky rock mass is prone to a sudden release of energy due to dynamic disturbance under confining load,resulting in sliding between rock strata.It is prone to anomalously low friction sliding instability for blocky rock mass,and then induces a new typical rock burst,that is anomalously low friction rock burst disaster.Its essence is the process of energy accumulation and unstable release.To reveal the energy characteristics of anomalously low friction effect of deep coal and rock,granite and coal rock mass were investigated using experimental research method.The self-developed test apparatus of anomalously low friction effect was used to simulate high in-situ stress by axial pressure and confining pressure loading and strong excavation disturbance by vertical vibration and horizontal impact loading.A complete rock block,a broken rock block and coal block were considered as the working block of anomalously low friction effect experiment.The experimental results were compared with the previous conclusions,which verify the rationality and feasibility of the experimental scheme.The total amount of kinetic energy per unit mass based on the horizontal displacement of working block was defined as the characteristic parameter of the energy variation of anomalously low friction effect.The influence of axial pressure,number of working blocks and lithology on the time and frequency domain curves of per unit mass kinetic energy of horizontal displacement of working blocks was analyzed.The relationships among mining depth,block fragmentation,lithology and block kinetic energy were presented.The results show that when the anomalously low friction effect occurs,the kinetic energy of the working block has the characteristics of accumulation effect,short-term peak value and intermittent.The degree of fragmentation and lithology are important factors that affect the total kinetic energy change of anomalously low friction rock burst.The experiment reproduces the process from the foreshock to the main shock of rock burst.It is found that when the energy of anomalously low friction rock burst is released,the block kinetic energy has a characteristic of frequency transferring from high frequency to low frequency.The main frequency is mainly in the low frequency range within 20 Hz.The results are basically consistent with the field observation of rock burst.The calculation method of the magnitude of rock burst retrieved from the energy release test was proposed.A case study at Hongyang No.3 Mine in China shows the result is very close to that in the field monitoring.