Abstract

The strength and the energy required for rock fracturing depend on the strain rate. However, the strain rate dependence of them under dynamic loading has not yet been fully understood. In this study, the author conducted static and impact three-point bending tests on specimens of andesite and gabbro, and explored the effect of strain rate on the bending strength and the absorbed energy required for fracturing. As a result of the tests, the bending strength of the rocks linearly increased from ca. 20 to 80 MPa with increase of the strain rate from 10–5 to ca. 50 s–1. The absorbed energy required for fracturing also increased from ca. 0.5 to 15 J per unit area with the increase of the strain rates. It increased rapidly and linearly with the strain rate in the strain rate region above 20 s–1. This change in the relationship between the strain rate and the absorbed energy required for fracturing would reflect a transition of the fracturing mechanism from the thermo-activation to the macro-viscosity.

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