INFLUENCE OF SCALE EFFECT AND HETEROGENEITY OF ROCKS TO DETERMINE THEIR STRENGTH PROPERTIES
The analysis and considers some aspects of the existence of a scale effect when testing rock samples to determine their strength properties. It is noted that in addition to determining the average values of strength important information is the value of the coefficient of variation as a characteristic of heterogeneity of rocks. The results of experimental studies of rock samples of different sizes when determining the ultimate strength in tension. According to test results there has been a sustained change (reduction) characteristics of the dispersion when increasing the length of the samples with an insignificant reduction of the value of the 214 average strength. For samples of marble and Sandstone, medium strength with a change in the size of the samples practically stays constant. Developed methodology and conducted strength tests of samples of small dimensions, whose diameter was ~6 mm. In specimens of small size, it should be noted a slight dispersion of values of indicators of the strength properties and consequently small values of the coefficient of variation. The data obtained during testing samples of small sizes of the studied rocks is quite associated with allowance for the size effect data for tests on standard samples, indicating the possibility of using this method for determining strength and elastic properties of rocks.