Abstract: To investigate mechanical parameters of fine-grained sandstone after high temperature, X-ray diffraction, scanning electron microscope (SEM) and uniaxial compression tests are conducted on fine-grained sandstone samples after 400~1 000 ℃ heating treatment. The correlation among mineral composition, structure characteristics and mechanical parameters of samples and temperatures is analyzed. The results show that: the polycrystalline occours in the fine-grained sandstone after high temperature treatments. Within 600 ℃, quartz content in the sample increases with increasing temperature, crystal diffraction enhances, and melting and recrystallization phenomenon can be observed clearly when the temperature is 600 ℃. Above 600 ℃, quartz content reduces with increasing temperature, the intensity of crystal diffraction is weakened, the crack quantity, the width and length increase, and cracks can be divided into the crack through the particles and along the grain boundary. The temperature of 600 ℃ is the critical temperature of quartz crystalloblast approximately. Within the range of 400 ℃ to 800 ℃, longitudinal wave velocity of the sample linearly decreases with the temperature. The sample strength is strengthened under 600 ℃, but the sample strength is weakened over 600 ℃. Thus, 600 ℃ can be used as a threshold temperature of strength conversion of samples. Within 400 ℃, elastic modulus and deformation modulus of samples increase slightly with the temperature increasing, and initial modulus and peak strain remain basically. However, deformation parameters of samples decrease with the temperature increasing above 600 ℃, and peak strain increases monotonically with temperature increasing above 400 ℃. The deformation parameters of fine-grained sandstone samples are more sensitive to the high temperature.

Key words: rock mechanics, high temperature, fine-grained sandstone, X-ray diffraction, mineral composition, mechanical parameters