Dynamics characteristics of gas-bearing coal under shock load

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.