层理煤岩动态破坏能量变化规律及损伤特征

Dynamic Failure Energy Change and Damage Characteristics of Bedding Coal Rock

利用Φ50 mm霍普金森压杆试验系统,对平行、垂直两种层理煤岩展开单轴冲击压缩试验,探讨不同应变率下层理煤岩动态破坏的能量变化规律和损伤演化特性,并引入裂纹扩展系数K分析其能量耗散全过程,以期更好地为层理煤岩开采破碎、灾害防治提供参考。研究表明:层理煤岩应变率效应明显,且存在特征界限响应应变率;随着应变率的增大,层理效应对煤岩力学特性参数及能量变化规律影响呈减弱趋势。垂直层理方向加载能够较大地抑制能量吸收与裂纹扩展,沿层理面方向加载可以有效提升煤岩破碎效果。基于能量耗散理论定义的损伤变量随时间呈S型增长,抗压强度对应的损伤变量随应变率呈线性减小,且平行层理煤岩减小速率较垂直层理煤岩大。

In order to explore the energy change law and damage evolution characteristics in dynamic failure of bedding coal rock under different strain rates,theΦ50 mm Hopkinson Pressure Bar test system was used to perform the uniaxial impact compression test in Parallel and vertical bedding coal rock,and the crack growth coefficient K was introduced to analyze the whole energy dissipation process.It could provide reference for the mining,crushing and disaster prevention of bedding coal.Research shows that the effect of strain rate is obvious,and there is a strain rate limit in the characteristic response.With the increase of strain rate,the influence of bedding effect on the change law of mechanical characteristic parameters and energy in coal rock decreases.Loading perpendicular to bedding direction can restrain energy absorption and crack propagation greatly,and loading along bedding plane can effectively enhance the effect of coal rock fragmentation.Based on the theory of energy dissipation,the damage variable is defined and increases in an S-shape with time.The damage variable corresponding to the compressive strength decreases linearly with the increase of strain rate,and the decrease rate of parallel bedding coal is larger.