采用分离式霍普金森压杆(SHPB)实验系统对不同冲击速度下煤岩试样应变率变化规律、动态力学特性及其变形破坏特征进行了测试,探讨了煤岩动态力学本构模型。实验结果表明,煤岩试样的加载应变率与冲击速度整体上呈正相关关系,且不同冲击速度下煤岩试样的力学响应特征均具有分段性,可根据响应特征的差异将煤(岩)试样在低-中-高冲击速度下的变形依次划分为压密变形、塑性变形、塑性软化(硬化)变形3种类型;煤岩试样的破坏特征均具有明显的应变率相关性,在低冲击速度下,试样均呈脆性破坏形式,随着冲击速度的增加,试样的延性破坏特征逐渐显现。在分析煤岩试样应力-应变本构关系及动态破坏特征的基础上建立了包含低-中-高应变率响应的粘弹性损伤本构模型,应用结果表明,与实测曲线相比模型拟合曲线拟合精度高,验证了所建模型的有效性与合理性。

The variation of strain rate,dynamic mechanical properties and deformation and failure characteristics of coal / rock samples under different impact velocities were investigated by the Split Hopkinson pressure bar(SHPB) test system,and a coal and rock dynamic mechanics constitutive model was discussed. The results show that there is a posi- tive correlation between the loading strain rate and the impact velocity of coal / rock samples,and the coal / rock samples have obvious phased mechanical response characteristics under different impact velocities. According to the difference of impact velocity,the stress-strain curves are divided into three types of compact deformation,plastic deformation, plastic softening deformation or plastic hardening deformation. In addition, the fracture characteristics of coal / rock samples all have significant strain rate dependence. Under low impact velocity,the samples are in the form of brittle failure. With the increase of impact velocity,the ductile fracture characteristics of samples gradually appear. Besides, based on the stress-strain constitutive relations and dynamic failure characteristics of coal / rock samples,a viscoelastic damage constitutive model with low-medium-high strain rate response was proposed. The results of numerical simula- tion show that the simulated curve has a good fitting accuracy with the measured curve,which proves the validity and rationality of the viscoelastic damage constitutive model with low-medium-high strain rate response.