Experimental study on dynamic mechanical properties of red sandstone under low temperatures

The dynamic mechanical properties and fracture fractal characteristics of saturated red sandstone under low temperatures are investigated by split Hopkinson pressure bar ( SHPB) technique and fractal theory,the influence of negative temperature change on dynamic strength performance and deformation law has been analyzed. Combined with the SEM scanning experiment,the microscopic fracture mechanism of saturated frozen red sandstone on the wave prop- agation has been studied. It is shown that the negative temperature changes significantly affect the dynamic mechanical properties and the fractal characteristics of red sandstone. The dynamic strength of red sandstone first increases and then decreases with the temperature reduction (25 - - 40 ℃ ),shaped like a “ 几” glyph,however,the peak strain shows a trend of first decreases and then increases,the test results are very different from the static load test results of frozen rock. The fractal dimension of red sandstone at 25,-5,-10,-20,-30,-40 ℃ are respectively 2. 37,2. 12,2. 29,2. 35,2. 41,2. 44,and the fractal calculation results are consistent with the test screening results. With the observa- tion and analysis of red sandstone fracture morphology,the final fracture of red sandstone at low temperature is found in clay cement or its boundary with mineral particles,red sandstone fracture morphology is relatively complicated under the condition of normal temperature,it is difficult to see the regularity,however,after introducing the low temperature gradient,the fracture morphology of the clay cement and mineral particles gradually show the regularity. It is concluded that the properties and fracture properties of cementitious materials have a more significant influence on the mechanical properties of red sandstone.