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浸水煤体静动力学特性与宏细观防冲机制

Static and dynamic mechanical properties and macro-micro coalburst prevention mechanisms of water-immersed coal

  • 摘要: 水化作用弱化冲击倾向性煤体宏细观力学性质,改善煤体应力波能量折反射能力,降低注水巷道冲击释能危险性。为探究水化作用下冲击倾向性煤体能量演化机制,开展了不同含水率下单轴压缩、冲击加载试验,基于能量原理分析了不同含水率冲击倾向性煤体动静载能量演化规律。利用电镜扫描和X射线衍射设备检测了冲击倾向煤体冲击破裂面粗糙度分形特征以及元素占比,揭示了含水率对煤体细观冲击破裂面粗糙性和矿物元素质量的影响规律,探讨了冲击应力波作用下冲击倾向性煤体浸水增裂防冲机制。结果表明:① 从干燥到饱水状态,动静压缩下冲击倾向性煤体破坏裂纹数量增多和曲折性增强,脆性减弱,韧性塑性显著增强。强冲击倾向性煤相较于弱冲击倾向性煤破坏更剧烈,裂纹相对较少。② 提高含水率削弱了冲击倾向性煤体动静载弹性应变能积聚能力,总释放能量减少。冲击动载下弱冲击倾向煤反射能占比从55%增至70%,透射能占比从9%衰减至3%,强冲击倾向煤反射能占比从24%增至50%,透射能占比从40%衰减至10%。③ 加强水化作用使冲击倾向性煤体破裂面的粗糙度和分形维数呈下降趋势,弱化了局部细观裂纹产生的能耗,继而相同冲击动能下冲击倾向煤体冲击裂纹数量增加,应力波在微裂纹中产生更多折射和反射路径,冲击能量在折反射中快速衰减,最终降低冲击释能危险性。

     

    Abstract: Hydration weakens the macro-mesoscopic mechanical properties of burst-prone coal, enhances the stress wave energy reflection-refraction capability of the coal, and reduces the risk of impact energy release in water-injected roadways. To investigate the energy evolution mechanism of burst-prone coal under hydration, uniaxial compression and impact loading tests at different moisture contents were conducted. Based on energy principles, the static and dynamic energy evolution laws of burst-prone coal with varying moisture contents were analyzed. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to detect the fractal characteristics of roughness and elemental composition on the impact fracture surfaces of burst-prone coal, revealing the influence of moisture content on the roughness of mesoscopic impact fracture surfaces and mineral element content. The mechanism of water-induced crack propagation and coalburst prevention in burst-prone coal under impact stress waves was discussed. Results show: ① From dry to saturated states, the number and tortuosity of failure cracks in burst-prone coal under static-dynamic compression increase, with reduced brittleness and significantly enhanced ductility and plasticity. Strong burst-prone coal exhibits more intense failure and fewer cracks compared to weak burst-prone coal. ② Increasing moisture content weakens the elastic strain energy accumulation capacity of burst-prone coal under static and dynamic loading, reducing the total released energy. Under impact loading, the reflected energy ratio of weak burst-prone coal increases from 55% to 70%, and the transmitted energy ratio decreases from 9% to 3%; for strong burst-prone coal, the reflected energy ratio increases from 24% to 50%, and the transmitted energy ratio decreases from 40% to 10%. ③ Enhanced hydration causes the roughness and fractal dimension of fracture surfaces in burst-prone coal to decrease, weakening the energy consumption of local mesoscopic crack generation. Consequently, at the same impact kinetic energy, the number of impact cracks in burst-prone coal increases, creating more reflection and refraction paths for stress waves in micro-cracks. Impact energy rapidly attenuates through reflection-refraction, ultimately reducing the risk of impact energy release.

     

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