Experimental investigations on loading-rate dependency of compressive and tensile mechanical behaviour of hard rocks

Abstract

Effects of loading rate on mechanical behaviour of brittle rocks are of great importance for stability assessment of underground structures. Brazilian splitting tension tests were performed under different loading rates ranging from 0.001 to 10 kN/s. The tensile strength increased with the increasing of the loading rate. There were clear transgranular microcracks in the specimen with loading rate of 10 kN/s, but intergranular microcracks in the one of 0.001 kN/s. Uniaxial compression tests were also performed under different loading rates. All the stress–strain curves under loading rates of axial stress ranging from 0.05 to 10 MPa/s show the typical mechanical responses of brittle rocks. The uniaxial compression strength and elastic modulus increased with the increasing of loading rate. The failure mechanism under uniaxial compression was similar to the Brazilian splitting tension tests. With the increasing of loading rate, intergranular microcracks became dominant instead of transgranular microcracks.