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.