Effect of Characteristic Impedance in Estimating Specific Energy and Average Fragment Size at High Strain Rates of Some Peridotitic Rock Materials at Laboratory Scale

Abstract

In this study, the application of characteristic impedance in estimating specific energy and average fragment size of rocks was investigated during rock breakage at high strain rates. To achieve this, rock specimen was prepared in accordance with recommendations of the International Society for Rock Mechanics and broken at high strain rates using the split Hopkinson’s pressure bar system. Results reveal that although strain rate is well related to specific energy and average fragment size of broken rocks, the product of characteristic impedance and strain rate is more reliable for estimating the forementioned parameters. In addition, strain rate and dissipated energy generally increase at higher incident energies while the average fragment size of broken rocks reduces at higher strain rates. Based on these findings, more studies on indirect estimation of energy requirement for rock breakage to desired average fragment sizes is recommended from the product of characteristic impedance and strain rate.

Experimental Investigation on the Influence of Wave Impedance on Dynamic Mechanical Response of Granites undergone High Temperature

“…That is, under the same test conditions and the same incident wave, the stress wave propagation process, stress history, loading rate, and strain rate of rock samples with different wave impedances are different. At the same time, relevant research shows that the dynamic mechanical properties of rock materials have an obvious rate effect. − Therefore, the dynamic mechanical response of different rock samples under the action of the same incident wave must be affected by the wave impedance. The analysis shows that there is a progressive influence relationship between rock wave impedance, stress wave propagation characteristics, strain rate/stress history, and dynamic mechanical response, that is, the magnitude of rock wave impedance affects the propagation and attenuation process of stress wave in the rock, resulting in changes in its strain rate history and stress history, and the rock dynamic mechanical response will inevitably be affected by its loading process and rate effect.…”