Experimental investigation on loading rate effect of sandstone after high temperature under uniaxial compression

The temperature is a very important factor affecting the physical and mechanical properties of rock. Uniaxial compression tests on sandstone after high temperature with six temperature levels between 25℃ to 800℃ under different loading rates are conducted to investigate the influence of temperature on loading rate effect. The results show that the physical properties of sandstone after high temperature appear to have a certain degradation, and that the density and longitudinal wave velocity respectively decrease by 5.89% and 73.72% with temperature rising from 25℃ to 800℃. With the increase of the temperature, the peak strength and elastic modulus decrease little by little, but the peak strain increases gradually, and the evolutionary process of the peak strength along with the temperature is strongly influenced by the loading rate. The peak strength and peak strain of sandstone after high temperature have an obvious loading rate effect, and they obey the positive linear relationship. The correlation parameter A characterizes the impact degree by loading rate, and with the increase of temperature, parameter A first decreases and then increases. The failure mode of sandstone transforms from mixing failure of tensile and shear gradually into a single shear failure with the increase of the temperature and loading rate, the damage degree becomes increasingly more serious, and the fractal dimension also increases gradually.