Study on tensile strength and size effect of red sandstone after high temperature treatment

In recent years, issues of rock mechanics under high temperature have been highlighted with the rapid development of nuclear waste treatment and underground coal gasification projects, which has become a focus in the rock mechanics field currently. In order to investigate the influence of temperature and sample size on the tensile strength, Brazilian splitting tensile strength tests were conducted on sandstone disc samples with five kinds of temperature levels ranging from 20℃ to 800℃ and five kinds of thickness-diameter ratios ranging from 0.5 to 1.0. Experimental results show that loading-displacement curves of sandstone discs appear remarkable brittle characteristics. And the temperature plays a leading role in the development trend of the curves, while the effect of sample size is relatively weak. With the increase of temperature, tensile strength first increases gradually and then decreases sharply, and reaches the maximum at 400℃. The tensile strength of sandstones under same temperature presents a linear attenuation relationship with the thickness-diameter ratio, and the corresponding experiential formula is put forward as σt =-Aλ + B. Here, the parameter A describes the prominent level of materials affected by the size, which decreases first and then increases with the increase of temperature, and the size effect is mostly unconspicuous at 400℃. The parameter B is the tensile strength value of materials when the sample size is infinitesimal to the ideal plane, which first increases slowly and then decreases gradually, with the maximum value also reaches at 400℃. ©, 2015, Academia Sinica. All right reserved.