Dynamic mechanical behavior and mesoscopic analysis of two layered sandstone after high temperature

In order to study the anisotropic characteristics of layered sandstone in dynamic and meso-structure,dynamic compression of layered sandstone after high-temperature heating was tested by large-diameter ( ϕ100 mm) SHPB. Then the fracture surfaces were tested by the scanning electron micro-scope ( SEM) so as to analyze the features of fracture morphology as well as the law of energy consumption and to conduct the numerical analysis of the extracted micro-crack network. According to the test results,the dynamic mechanical properties of anisotropic sandstone after high temperature are affected by the velocity of impact bullet,temperature effects and bedding anisotropy. As the veloc-ity of impact bullet rises,the peak intensity of sandstone increases,peak strain increases,and variable model increa-ses. As temperature rises,the peak intensity of sandstone decreases,peak strain increases,while variable model decrea-ses. Parallel layered sandstone shows a better integration than vertical samples in terms of peak intensity,peak strain and variable model. Fractures under high strain rates show a worse integration than the ones under low strain rates, with a rougher morphology. With a temperature under 400 ℃ ,the fractures mainly consist of inter-granular fracture and trans-granular fracture,presenting brittle fracture. With a temperature of 800 ℃ ,fractures partially present plastic frac-ture and ductile fracture,apart from the two former modes. The energy consumption of broken sandstone is higher un-der high strain rates than that under low strain rates. There is obvious anisotropy among numbers,areas and shapes of fractures. In general,the fracture number in horizontal bedding samples is more than that in vertical bedding samples. The micro-fracture rate curve of horizontal bedding samples is lower than that in vertical bedding samples. Fracture shapes in vertical bedding samples are generally more regular than those in horizontal bedding samples. Fracture shapes of dynamic broken samples after high temperature tend to be regular.