EXPERIMENTAL RESEARCH ON MECHANICAL PROPERTIES OF LIMESTONE AND SANDSTONE UNDER HIGH TEMPERATURE

The mechanical properties of limestone and sandstone under high temperature were investigated by the experiment device used to heat rock designed by ourselves and servo-control testing machine RMT-150C. The results show that the longitudinal wave velocity of two kinds of rocks gradually reduced with temperature increasing. The complete curve of stress and strain under uniaxial compression went through 4 stages, namely densification, elasticity, yielding and failure. They both displayed brittle fracture after reaching peak strength, with the sandstone rupturing and the limestone showing failure like a bundle of grass. The high temperature weakened their strength. Their peak stresses reduced with temperature increasing. At 700 ℃, the peak strength of limestone decreased by 84.59 %, while that of sandstone only decreased by 22 %. Their peak strain increased with temperature increasing, but differed in details. For limestone, its peak strain increased by 30.57 % at 500 ℃, but almost kept unchanged at the higher temperature, and even shaw a little decrease at 700 ℃.For sandstone, however, the peak strain increased by 80.63 % at 700 ℃, displaying a connection with the variation of microstructure. With temperature increasing, their elastic modulus and deformation modulus decreased. At 700 ℃, limestone decreased by 86.8 % in elastic modulus and by 83.9 % in deformation modulus, while sandstone decreased by 46.94 % in elastic modulus and by 53.06 % in deformation modulus.