Abstract: Spiral CT（Computerized Tomography）and intelligent ultrasonic velocimeter were used in the non-destructive testing of five sandstone samples of different scales under the condition of drying and of different degrees of saturation. The test results show that water absorption of vacuum saturation method is a bit bigger than that of natural immersion method(D = 50 mm); saturated water absorption and the height of specimen are almost linearly related; the water absorbing ability of the specimen is weakest when the height to diameter ratio(h/D) is maximum and its value is 3.5, while it is relatively strong when the size ratio in the two directions is near two; duo to the anisotropy of rock caused by its natural defects, the smaller specimen size is, the higher anisotropy index will be, and the macro-uniformity of the specimen will be obvious when the size of it is large enough; both of the macro mechanical parameters and micro mechanical parameters of sandstone are of scale effect, The variation of the elastic modulus of the rock specimen is huge when its height to diameter ratio is less than two(h/D＜2.0) and the calculation elastic modulus of the rock specimen increases slowly with the increase of height when its height to diameter ratio is greater than or equal to two(h/D≥2.0). Nondestructive testing parameters’ scale effect equation of sandstone of different moisture contents is obtained in this article; the formula shows that squares of the test specimen’s longitudinal wave velocity and numbers have inverse correlation to the water absorption effect of sandstone; the result is of certain guiding significance for the research of water rock interaction when considering the scale effect of the specimens.

Key words: ultrasound-CT, saturated water absorption, scale effect, nondestructive testing, micro-characteristics