高温作用下页岩动态力学特性及微观损伤特征研究

Study on the Dynamic Characteristics and Microscopic Damage Features of Shale Under High Temperature

温度和冲击载荷耦合作用下页岩微观损伤特征和宏观力学性能关系密切,为研究高温作用下页岩的动态力学特性及微观损伤特征,基于分离式霍普金森压杆(SHPB)实验系统,对常温(25℃)和高温后(200℃、400℃、600℃、800℃)的页岩试样开展动态冲击压缩实验,并利用X射线衍射(XRD)和扫描电镜(SEM)测试手段对不同温度作用后的页岩试样进行微观结构分析。结果表明:在相同冲击气压条件下,试样动态抗压强度、弹性模量随温度升高逐渐降低,页岩强度劣化,破碎程度加剧。温度一定时,随着冲击气压的提高,试样强度和变形均不断增大,呈现出明显的应变率强化效应,且冲击气压越大温度的劣化效应越显著。页岩试样随冲击气压增大穿晶断裂现象增多,而随着温度的升高,400℃时页岩动态力学性能发生剧变,600~800℃时出现韧窝和滑移分离为代表的塑性破坏特征,温度导致页岩矿物组成结构改变是致使其力学性能变化的主要原因。

The microscopic damage characteristics and macroscopic mechanical properties of shale are closely related under the coupling effect of temperature and impact load.To study the dynamic characteristics and microscopic damage features of shale under high temperature,dynamic impact compression experiments were conducted on shale samples at room temperature(25℃)and after high−temperature treatment(200℃,400℃,600℃,and 800℃)using the Split Hopkinson Pressure Bar(SHPB)experimental system.X−ray diffraction(XRD)and scanning electron microscopy(SEM)were employed to analyze the microstructure of shale samples subjected to different temperatures.The results showed that under the same impact pressure conditions,the dynamic compressive strength and elastic modulus of the samples gradually decreased with increasing temperature,leading to the deterioration of shale strength and increased fragmentation.At a constant temperature,as the impact pressure increased,the strength and deformation of the samples continuously increased,exhibiting a significant strain rate strengthening effect,and the higher the impact pressure,the more pronounced the temperature deterioration effect.With the increase in impact pressure,the transgranular fracture phenomenon in shale samples increased,while with the rise in temperature,a dramatic change in the dynamic properties of shale occured at 400℃.At 600~800℃,plastic damage features represented by dimples and slip separation appear.The change in mineral composition structure caused by temperature was the main reason for the variation in the mechanical properties of shale.