高温后深部矽卡岩动力学特性及微观破坏机制研究

Dynamic mechanical properties and microscopic damage characteristics of deep skarn after high-temperature treatment

以深部700 m处矽卡岩为研究对象,采用分离式霍普金森压杆装置开展不同冲击气压(0.8,1.0,1.2 MPa)下常温和经历不同温度(200℃,400℃,600℃,800℃)作用后的岩石冲击压缩试验,研究深部岩石的高温动力学行为;借助SEM扫描电镜及XRD物相特征分析技术,探索矽卡岩在高温和动载作用下的微观破坏机制。结果表明:相同冲击气压作用下,随着温度的升高,矽卡岩强度劣化、延性增强;相同温度条件下,随着冲击气压的增大,矽卡岩强度和变形均增大,表现出明显的应变率效应。冲击气压增大或温度升高,矽卡岩破碎程度均越来越剧烈,破碎块度越来越小,800℃时破碎状态以颗粒较小的碎石和粉末状为主。内部组分及结构的变化是造成矽卡岩力学性能变化的主要原因,25℃~400℃矽卡岩主要为穿晶和沿晶断裂的脆性破坏;400℃~600℃为矽卡岩由脆性向塑性转化的阈值温度区间;600℃~800℃时则转变为韧窝和滑移断裂的塑性破坏。

The skarn at a depth of 700 m is taken as the research object to study the dynamic behaviors of deep rocks under high temperature.The impact compression tests at different impact air pressures(0.8,1.0 and 1.2 MPa)are carried out on the skarn at room temperature and after high-temperature treatment(200℃,400℃,600℃and 800℃)by using the split Hopkinson press bar experimental device.The fracture surface is observed by the SEM scanning electron microscope and XRD phase characteristic analysis technology to explore the micro-failure mechanism of the skarn under high temperature and dynamic load.The test results show that under the same impact air pressure,the strength of the skarn deteriorates and the ductility increases with the increase of temperature.And at the same temperature,both the strength and deformation of the skarn increase with the increase of impact pressure,showing obvious strain rate effect.With the increase of impact pressure or temperature,the crushing degree of the skarn becomes more and more intense,and the fragmentation becomes smaller and smaller,and especially smaller particles are mainly crushed at 800℃.The change of internal composition and structure is the main reason for the change of mechanical properties of the skarn.The brittle failure of the skarn is mainly transgranular and intergranular fracture at 25°C~400°C.400°C~600°C is the threshold temperature range of skarn transformation from brittle to plastic.When the temperature degree is up to 600°C~800°C,it transforms into dimple and slip fracture.