震动载荷下含瓦斯煤动力学特征

Dynamics characteristics of gas-bearing coal under shock load

  • 摘要: 为了研究震动载荷下含瓦斯煤动力学特性,建立了含瓦斯煤霍普金森压杆试验系统,考虑轴向静载、围压、瓦斯压力和动载荷冲击速度4个因素,开展了含瓦斯煤动力学试验,通过采集入射波、反射波和透射波信号,分析了震动载荷下含瓦斯煤动态应力应变曲线变化规律,研究了含瓦斯煤峰值强度和峰值应变与有效轴向静载、有效围压和动载荷冲击速度的关系。研究结果表明:震动载荷下含瓦斯煤动态应力应变曲线无压密阶段,初始加载应力就随应变呈“线弹性”增加趋势;随着应变进一步增加,应力变化先趋于平缓又快速增加,该曲线表现出“跃进”特性,这与炭在晶体微破裂中的作用有关;峰后试样未产生宏观破坏,弹性能释放造成应力应变出现“回弹”现象。含瓦斯煤峰值强度随有效轴向静载呈指数增加、随有效围压呈线性增加、随动载荷冲击速度呈先增加后减小;含瓦斯煤峰值应变随有效轴向静载呈线性增加、随有效围压呈指数衰减、随动载荷冲击速度增大而增加。震动载荷下含瓦斯煤应变率效应明显,在应变率低水平阶段,含瓦斯煤峰值强度和峰值应变随应变率增加而增加,超过临界应变率,含瓦斯煤峰值强度和峰值应变将保持稳定。该研究有助于完善含瓦斯煤动力学,为矿井动载荷诱导的含瓦斯煤动力灾害防治提供借鉴。

     

    Abstract: To study the dynamics characteristics of gas-bearing coal under shock load,the split Hopkinson pressure bar test system of gas-bearing coal (SHPB-GAS) was built. With the consideration of the factors of axial static load,confi- ning pressure,gas pressure and dynamic load impact velocity,the dynamics experiments were carried out. By collecting incident wave,reflected wave and transmission wave signals,the relationships between peak strength,peak strain and various factors were analyzed. The results showed that the dynamic stress-strain curves of gas-bearing coal were of no compaction stage,which showed linear elasticity characteristic at the initial loading stage. With the increase of strain, the stress changes tended to be gentle increase and then rapid increase,which was called " leap" characteristic. This was related with charcoal in coal crystal micro-fracture. After the stress-strain peak,the coal samples didn’t have macro rupture,so the stress-strain curves appeared “ rebound” phenomenon. The peak strength of gas-bearing coal in- creased exponentially with effective axial static load,increased linearly with effective confining pressure,and increased first and then decreased with the impact velocity of dynamic load. Peak strain of gas-bearing coal increased linearly with effective axial static load,decreased exponentially with effective confining pressure,and increased with the in- crease of impact velocity of dynamic load. The strain rate effects of gas-bearing coal were obvious under shock load. At the low level of strain rate,the peak strength and peak strain of gas-bearing coal increased with the increase of strain rate,and when it exceeded the critical strain rate,the peak strength and peak strain of gas-bearing coal would remain stable. This study is useful for improving the dynamics of gas-bearing coal,and provides a theoretical basis for the pre- vention and control of mine dynamic disasters of gas-bearing coal induced by dynamic load.

     

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