Abstract: Size effect is an unavoidable problem in rock mechanics experiment, and is directly related to the rationality of rock mechanics parameters. In previous studies on the size effect of rock splitting tensile strength, the influence of thickness-to-diameter ratio of rock specimen was mostly considered rather than the influence of rock sample diameter. In view of this, we performed Brazilian splitting tensile strength tests on specimens of five different diameters (25, 30, 50, 100, 150 mm). Results unveiled that: 1) at given thickness-to-diameter ratio, the tensile strength of rock sample declined from being sharply towards gently as the diameter augmented from 25 mm to 150 mm. When the diameter exceeded 50 mm, tensile strength tended to be stable. Such variation trend can be well fitted by exponential function. 2) The size effect of splitting tensile strength of rock is not only related to the thickness-to-diameter ratio, but also related to the diameter of rock specimen. According to previous research experience, we suggest that the thickness-to-diameter ratio around 0.3, and diameter more than 50 mm, in which case the size effect on splitting tensile strength can be well eliminated.

Key words: sandstone, Brazilian splitting, tensile strength, diameter, size effect