微波-水交互作用下富油煤岩渐进性破坏规律试验

Experiment on progressive failure law of tar-rich coal under microwave-water interaction

陕北富油煤储量大,其组分内含有较多页岩气,同时其内部裂隙少、致密、强度大,井下开采过程呈现“三大一快”,容易形成顶板大面积悬顶和其他次生灾害。常规治理顶板动力灾害的手段存在诸多不足,故此引入微波辐射,制作不同含水率的富油煤样,通过微波照射不同含水率下的富油煤,分析微波照射前后煤样的物理力学性质,研究微波作用下不同含水率煤样的裂隙扩展规律、煤样最终破坏形态和基于煤样碎块等效边长-质量下的分形维数。试验结果表明:(1)同一微波辐射条件下,煤岩试样能量积聚和耗散与含水率呈负相关,富油煤纵波波速平均下降幅度分别为4.22%,7.23%,11.76%,能量积聚和耗散进一步降低。(2)随着含水率增大,富油煤破坏模式由压剪破坏逐步转变为拉剪混合破坏,引入微波辐射,富油煤破坏程度继续增大,破坏模式由剪切破坏逐步转变为柱状拉伸破坏。相较于水,微波对煤样的改造作用更强,水的参与使得微波作用效果提升明显。(3)随含水率增大,分形维数呈现递减趋势,引入微波后,分形维数递减速率更为明显。因此两者对于分形维数递减均呈促进作用。揭示富油煤经微波与水交互作用下的渐进性破坏规律,为微波与水力交互压裂机制提供有效参考,为顶板动力灾害防治措施提供基础性理论支撑。

The tar-rich coal reserves in northern Shaanxi are large,and its components contain more shale gas.At the same time,its internal fissures are few,dense and strong,and the underground mining process presents“three big and one fast”,which is easy to form large-scale roof hanging and other secondary disasters.There are many shortcomings in conventional measures to control roof dynamic disasters.Therefore,microwave radiation is introduced to make tar-rich coal samples with different moisture contents.Through microwave irradiation of tar-rich coal samples with different moisture contents,analyze the changes of physical and mechanical properties of coal samples under microwave irradiation,and the crack propagation law,the final failure form of coal samples and the fractal dimension based on the equivalent side length-mass of coal samples under microwave irradiation are studied.The experimental results show that:(1)Under the same microwave radiation condition,the energy accumulation and dissipation of coal samples are negatively correlated with the water content,and the average longitudinal wave velocity of tar-rich coal decreases by 4.22%,7.23%and 11.76%respectively,and the energy accumulation and dissipation are further reduced.(2)With the increase of water content,the failure mode of tar-rich coal gradually changed from compression-shear failure to tension-shear mixed failure.With the introduction of microwave radiation,the failure degree of tar-rich coal continued to increase,and the failure mode gradually changed from shear failure to columnar tensile failure.Compared with water,microwave has a stronger effect on coal sample reforming,and the participation of water makes the effect of microwave obviously improved.(3)With the increase of water content,the fractal dimension shows a decreasing trend,and the decreasing rate of fractal dimension is more obvious after microwave is introduced.Therefore,both of them can promote the decrease of fractal dimension.The progressive failure law of tar-rich coal under the interaction of microwave and water is revealed,which provides an effective reference for the mechanism of microwave and hydraulic fracturing,and provides basic theoretical support for roof dynamic disaster prevention measures.