SAMPLE SIZE INFLUENCE ON STRESS-STRAIN PROPERTIES OF ROCKS
O. M. Usoltseva, P. A. Tsoi, V. N. Semenov
Chinakal Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Scale factor, strength, Young’s modulus, modulus of decrease
Abstract
The results of an experimental study of the influence exerted by the sizes of samples of hornfels, limestone, sandstone, siltstone and ore-bearing rocks on their stress-strain properties are presented. Tests were performed on cylindrical samples of 10, 30, and 100 mm in diameter under uniaxial compression and tension. It is shown that ultimate strength decreases as the sizes of hornfels, limestone, sandstone, and siltstone samples increase. For rocks containing viscous inclusions, there is a slight increase in strength with increasing sample size. The samples of smaller size exhibit brittle failure for all types of rocks, and failure viscosity increases with increasing sample size. An explanation of the obtained patterns of change in stress-strain characteristics depending on rock tendency to viscous or brittle failure, its structural and textural inhomogeneity from the standpoint of two types of scale effect - volumetric and surface, is given.
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