冲击载荷瞬时扰动原煤试样破裂演化及瓦斯放散特征研究

Fracture evolution and gas emission characteristics of raw coal samples subjected to instantaneous disturbance of impact loads

为了揭示冲击扰动煤体瞬时破坏及瓦斯异常涌出机制,采用含瓦斯煤霍普金森压杆试验系统,开展冲击载荷下三维含瓦斯煤冲击破坏及瓦斯放散测试,研究冲击载荷瞬时扰动下原煤试样破裂演化特征及瓦斯放散规律,分析轴向静载、围压、瓦斯压力和冲击载荷速度4个受载因子对初始最大瓦斯放散速度的影响。结果表明:在低围压或高冲击载荷条件下,三维含瓦斯煤呈现粉碎式破坏,其他试验条件下煤样呈现轴向拉伸破坏模式,裂纹尺度和数量随着轴向静载、围压、瓦斯压力和冲击载荷数值大小而有所不同;冲击载荷作用瞬间,原煤试样瓦斯放散速度瞬时达到最大,随后呈幂指数形式衰减;瓦斯放散持续时长基本在2.00 s之内,随受载因子变化而略有不同;冲击瞬间最大瓦斯放散速度随轴向静载呈指数函数增加,随围压呈线性降低,随瓦斯压力和冲击载荷速度呈线性增加趋势。通过单位尺度受载因子变化对原煤试样最大瓦斯放散速度的贡献度,确定影响煤体瓦斯放散的受载条件重要度为r(冲击载荷)>r(围压)>r(轴向静载)>r(瓦斯压力)。基于乌斯基诺夫式煤粒瓦斯放散模型,建立冲击扰动原煤瓦斯放散模型,对比不同冲击载荷速度下放散模型计算的放散速度理论值与实验值,变化趋势和重合度较好,说明该模型可以反映冲击载荷对原煤瓦斯放散的影响,可以用于采场冲击扰动煤体瓦斯异常放散的预测。研究成果将有助于揭示含瓦斯煤复合动力灾害形成机制,促进采场扰动煤体瓦斯异常涌出治理,保障深部煤炭资源安全高效绿色开采。

To reveal instant fracture of coal and abnormal gas emission at the disturbance of impact loads,the Hopkinson pressure bar test system of gas-bearing coal was used to carry out the tests about impact failure of threedimensional gas-bearing coal and gas emission subjected to impact loads.The fracture evolution of raw coal samples and gas emission laws under instantaneous disturbance of impact load were studied,and the effects of loaded factors such as axial static load,confining pressure,gas pressure and impact load speed to the initial maximum gas emission speed were analyzed.The results showed that the three-dimensional gas-bearing coal presented fragmentation failure under the condition of low confining pressure or high impact load,while the coal samples presented axial tensile failure mode under other test conditions,and the size and number of cracks varied with the axial static load,confining pressure,gas pressure and impact load.The gas emission speed of raw coal samples reached the maximum at the moment of impact load,and then decayed in the form of power exponent.The duration of gas emission was basically within 2.00 s,which varied slightly with the change of loaded factors.The maximum gas emission speed at the moment of impact increased exponentially with axial static load,decreased linearly with confining pressure,and increased linearly with gas pressure or impact load velocity.Through the contribution of the loading factor change in unit scale to the maximum gas emission speed,it was determined that the importance of loading conditions affecting gas emission was r(impact load)>r(confining pressure)>r(axial static load)>r(gas pressure).Based on gas emission model of coal particle expressed by Uskinov,the gas emission model of raw coal under impact disturbance was established.By the comparison of theoretical and experimental values about gas emission speed at different impact load velocity,their change trends and coincidence degree were good.This phenomena indicated that this model could reflect the effects of impact load to gas emission of raw coal samples,and be used to predict abnormal gas emission caused by impact disturbance in the stope.These achievements will help to reveal the formation mechanism about compounded dynamic disaster of gas-bearing coal,and promote the treatment of abnormal gas emission caused by stope disturbance,which will ensure deep coal resources mining in safe,efficient and green way.