Experimental study of mechanical properties of sandstone at high temperature

Mechanical properties of rock at high temperature are of importance for structure design and safety assessment in underground rock engineering. Brazilian disc test, axial compressive test and three-point bending test are adopted to determine the tensile strength sigma(t), uniaxial compressive strength sigma(c), elastic modulus E and Mode I fracture toughness K-Ic of sandstone at high temperature. Test results show that all of these values (sigma(t), sigma(c), E and K-IC) are linearly increased with the increasing temperature below a certain temperature, 200 degrees C or 250 degrees C, and decreased above this temperature. The linear equations are sigma(t)=0.010 9T+2.322, sigma(c)=0.181 9T+63.138, E=0.004 9T+10.498 and K-tc=0.003 1T+0.60, respectively. Mineral compositions and microstructures of natural rock material have great influences on its mechanical properities at high temperature. Dominance of drying or microcracking would lead to the improvement or degradation of mechanical properities of rock.