Assessment of the loading rate impact on the uniaxial compressive strength of hard rocks and their failure behavior

Abstract

When studying physical and mechanical properties of rocks, one of the main parameters to be determined is their uniaxial compressive strength. During laboratory experiments, the value of this parameter can be influenced by both loading conditions and the shape of the prepared samples. By studying the impact of these factors, it is possible to give an adequate assessment of changes in the strength of rocks, as well as to predict their failure behavior. The paper presents the results of experimental studies of hard rocks from the Kola region deposits under uniaxial compression. The values of the rock strength at loading rates from 0.01 to 50 kN/s were established. On the basis of the obtained data it was revealed that the V.A. Fokin criterion can be used to determine the rated strength of rocks. It is shown that the values of uniaxial compressive strength of brittle elastic rock (urtite) and non-brittle elastic-plastic rock (carbonatite) will also increase with the increasing loading rate. It is established that for hard rocks prone to dynamic failure, an increase in the loading rate will lead to an increase in the intensity of their failure. Increasing the loading rate for non-brittle elastic-plastic rocks can cause them to start failing dynamically. The obtained conclusions indicate that the failure behavior of rock samples depends on the time factor of loading.